Introduction to Plant Pathology Answers PDF

Introduction to Plant Pathology Answers 1. Who first observed myxomycetes that cause clubroot disease of cabbage? A. Erwin Smith B. L.R. Jones C. A. Mayer D. Woronin Answer: Woronin (D) Woronin was the first to observe myxomycetes causing clubroot disease in cabbage. 2. What was d...

Introduction to Plant Pathology Answers 1. Who first observed myxomycetes that cause clubroot disease of cabbage? A. Erwin Smith B. L.R. Jones C. A. Mayer D. Woronin Answer: Woronin (D) Woronin was the first to observe myxomycetes causing clubroot disease in cabbage. 2. What was discovered by Burrill in 1878 regarding bacteria? A. They have no role in disease. B. They cause fire blight of pear and apple. C. They produce toxins killing plant cells. D. They are responsible for crown root gall. Answer: They cause fire blight of pear and apple. (B) Burrill discovered that bacteria caused fire blight disease in pear and apple. 3. Which plant defense activator was the first commercial synthesized? A. Agrobacterium B. Actigard C. Systemic acquired resistance D. Pectic enzymes Answer: Actigard (B) Actigard was the first commercial synthesized plant defense activator. 4. What did Ivanowski demonstrate in 1982 regarding tobacco mosaic disease? A. Bacteria are the primary agents. B. Protozoa initiate disease. C. Fungi cause cell death. D. Viruses are the primary agents. Answer: Viruses are the primary agents. (D) Ivanowski demonstrated through filtration that viruses were implicated in tobacco mosaic disease. 5. Which of these pathogens was linked to the soft rot of vegetables in 1905? A. Viruses B. Protozoa C. Fungi D. Bacteria Answer: Bacteria (D) L.R. Jones reported the involvement of cytolytic enzymes from bacteria in soft rot of vegetables. 6. What significant enzyme was discovered in 1915 that contributes to disease formation? A. Pectic enzymes B. Cytolytic enzymes C. Pathogenic enzymes D. Toxins Answer: Pectic enzymes (A) Pectic enzymes were found to be significant in disease formation in 1915. 7. What organism did Stahel discover infecting coffee in 1931? A. Fungi B. Protozoa C. Bacteria D. Viruses Answer: Protozoa (B) Stahel discovered that protozoans infect coffee. 8. Which pathogen was shown to produce victorin that blighted oats in 1947? A. Pseudomonas tabaci B. Agrobacterium tumefaciens C. Bipolaris sp. D. Helminthosporium Answer: Bipolaris sp. (C) Helminthosporium (Bipolaris) sp. was shown to produce victorin causing blight in oats. 9. What is the term for the clustering of roots, flowers, fruits, or twigs around a common focus? A. Mummification B. Mosaic C. Fasciculation D. Pitting Answer: Fasciculation (C) Fasciculation refers to the clustering of various plant structures around a common point. 10. Which symptom is characterized by the leaf veins appearing translucent or pale while the rest of the leaf maintains its normal color? A. Mosaic B. Mottling C. Vein clearing D. Gummosis Answer: Vein clearing (C) Vein clearing denotes a distinct visual symptom where only the leaf veins become pale or translucent. 11. What does virescence indicate in plant tissues? A. Oozing of gum from wounds B. Crowding of foliage C. Translucent leaf veins D. Development of chlorophyll Answer: Development of chlorophyll (D) Virescence is the process involving the development of chlorophyll in places where it is typically absent. 12. Which of the following is described as a pocked appearance due to depressions on surface tissues? A. Phyllody B. Rosetting C. Pitting D. Flecks Answer: Pitting (C) Pitting refers to the formation of small depressions or pits on the surface of various plant parts. 13. What characteristic defines wilting that is caused by an infectious agent? A. Irreversible death of the plant B. Crowding of foliage in a rosette C. Temporary recovery upon watering D. Development of variegated patterns Answer: Irreversible death of the plant (A) Wilting that results from an infectious agent can lead to the permanent death of the plant if not controlled. 14. What is the primary objective of plant pathology? A. To improve plant breeding techniques B. To prevent or minimize plant diseases C. To increase the aesthetic appeal of plants D. To promote the use of chemical fertilizers Answer: To prevent or minimize plant diseases (B) The objective of plant pathology is to prevent or minimize plant diseases to ensure quality and quantity of crops. 15. Which type of disease caused the death of 10 million peach trees in the Eastern U.S. and Russia? A. Peach yellows B. Root knot C. Soybean cyst nematode D. Sugar beet cyst nematode Answer: Peach yellows (A) Peach yellows is a phytoplasmal disease linked to the significant loss of peach trees. 16. Which of the following regions experienced millions of pear trees killed due to pear decline? A. Pacific coast states & Canada B. Worldwide C. Eastern U.S. and Canada D. Northern Europe and Asia Answer: Pacific coast states & Canada (A) Pear decline has been particularly devastating on the Pacific coast states and Canada. 17. What percentage of crops is estimated to be lost to plant diseases? A. 30% B. 20% C. 5.2% D. 14.1% Answer: 14.1% (D) Approximately 14.1% of crops are lost to plant diseases, leading to significant economic impacts. 18. What economic loss is attributed to plant diseases annually worldwide? A. $100 million B. $220 billion C. $500 billion D. $1 billion Answer: $220 billion (B) The total annual crop loss due to plant diseases is about $220 billion. 19. What is the condition characterized by the excessive swelling of the bark above an injury? A. Sarcody B. Bleeding C. Blight D. Canker Answer: Sarcody (A) Sarcody refers to the abnormal swelling of the bark above an injury. 20. Which nematode disease is known for continuous losses on soybeans in Asia and North & South America? A. Root knot B. Soybean cyst nematode C. Peach yellows D. Sugar beet cyst nematode Answer: Soybean cyst nematode (B) Soybean cyst nematode is a significant pest resulting in ongoing losses for soybean crops. 21. Which term describes the yellowing of plant leaves not caused by light deficiency? A. Etiolation B. Curling C. Damping off D. Chlorosis Answer: Chlorosis (D) Chlorosis is specifically noted as yellowing that does not result from inadequate light. 22. Which disease caused continuous severe annual losses on sugar beets in Northern Europe and the Western U.S.? A. Sugar beet cyst nematode B. Root knot C. Cereal rusts D. Peach yellows Answer: Sugar beet cyst nematode (A) The sugar beet cyst nematode significantly affects sugar beet crops with severe annual losses. 23. What is the name for the localized necrotic area commonly referred to as a lesion? A. Scab B. Spot C. Blotch D. Damping off Answer: Spot (B) A spot refers to a localized necrotic area, also known as a lesion. 24. What type of diseases result in frequent severe epidemics and huge annual losses globally? A. Nematode diseases B. Fungal diseases C. Phytoplasmal diseases D. Bacterial diseases Answer: Fungal diseases (B) Fungal diseases, such as cereal rusts, are responsible for frequent severe epidemics causing extensive damages. 25. Which phenomenon involves the rotting of seedlings prior to emergence? A. Damping off B. Savoying C. Blight D. Die-back Answer: Damping off (A) Damping off is the term used for the rotting of seedlings before they can emerge. 26. What is a common type of crop loss caused by plant diseases? A. Increased pest resistance B. Reduction in yield C. Market price decrease D. Loss of soil fertility Answer: Reduction in yield (B) Reduction in yield is a primary indicator of crop loss due to plant diseases. 27. What condition results in large, irregular spots on leaves or fruits due to necrosis? A. Scab B. Canker C. Curling D. Blotch Answer: Blotch (D) Blotch refers to large, irregular spots on foliage or fruit resulting from necrotic injury. 28. Which of these diseases is responsible for continuous losses on vegetables worldwide? A. Peach yellows B. Root knot C. Cereal rusts D. Sugar beet cyst nematode Answer: Root knot (B) Root knot is a nematode disease that leads to ongoing losses in vegetable production worldwide. 29. What symptom is characterized by a perforated appearance of leaves? A. Callus B. Curling C. Shot-hole D. Scab Answer: Shot-hole (C) Shot-hole disease gives leaves a perforated appearance due to local lesion dropout. 30. Which term refers to overgrowth of tissue formed due to injury? A. Savoying B. Chlorosis C. Canker D. Callus Answer: Callus (D) Callus is the term for the overgrowth of tissue as a response to injury. 31. What term is used to describe the drying backward from the tip of a plant? A. Curling B. Etiolation C. Die-back D. Chlorosis Answer: Die-back (C) Die-back refers to the drying that occurs from the tips of plant tissues. 32. Which disease symptom involves extensive sudden death of host tissues? A. Canker B. Blotch C. Blight D. Shot-hole Answer: Blight (C) Blight is characterized by the sudden and extensive death of host tissues. 33. Which of the following terms denotes the sunken necrotic area with a cracked border? A. Sarcody B. Bark scaling C. Blight D. Canker Answer: Canker (D) Canker is identified as a sunken, necrotic area with a distinctive cracked border. 34. What type of resistance is characterized by being strong but effective only against one or a few pathogen races? A. Hypersensitivity resistance B. Horizontal resistance C. Phytoalexin resistance D. Vertical resistance Answer: Vertical resistance (D) Vertical resistance is controlled by a few major resistance genes and is specifically targeted. 35. Which plant defense mechanism involves the immediate death of attacked and adjacent cells to isolate the pathogen? A. Epidemiology B. Horizontal resistance C. Hypersensitivity D. Vertical resistance Answer: Hypersensitivity (C) Hypersensitivity is a defense response that effectively isolates the pathogen by causing cell death. 36. What did Mills develop in 1944 to predict infection by the apple scab fungus? A. A model for pathogen genetics B. A table correlating rain duration and temperature C. A new species of apple resistant to scab D. A treatment for infected apple trees Answer: A table correlating rain duration and temperature (B) Mills' table specified the necessary rain durations at various temperatures for infection by the fungus. 37. Which of the following types of resistance is controlled by many 'minor' resistance genes and is effective against all races of a pathogen species? A. Horizontal resistance B. Epidemiological resistance C. Phytoalexin resistance D. Vertical resistance Answer: Horizontal resistance (A) Horizontal resistance is generally weaker but universally effective against all races of a pathogen. 38. Which disease caused the eradication of millions of trees in Florida during the 1910s and again in the 1980s and 1990s? A. Phytophthora rot B. Apple scab C. Citrus canker D. Fire blight Answer: Citrus canker (C) Citrus canker is known to have caused significant tree loss in Florida during those periods. 39. What component is suggested to contribute to disease resistance in some plants starting in the 1960s? A. Hormones B. Phytoalexins C. Pathogen inhibitors D. Major resistance genes Answer: Phytoalexins (B) Phytoalexins are compounds that help confer disease resistance in certain plants. 40. What does the term 'plant pathology' refer to? A. The genetic modification of plants to resist diseases B. The cultivation methods to prevent disease C. The treatment of infected plants D. The study of plant diseases and their causes Answer: The study of plant diseases and their causes (D) Plant pathology is the scientific study of organisms and environmental factors causing disease in plants. 41. Which of the following elements is NOT associated with hypersensitivity as a plant defense mechanism? A. Isolation of the pathogen B. Production of phytoalexins C. Sensitivity of attacked cells D. Immediate cell death Answer: Production of phytoalexins (B) While hypersensitivity involves immediate cell death and isolation, the production of phytoalexins is a separate resistance mechanism. 42. E.Gaümann's proposal in 1946 primarily related to which aspect of plant disease resistance? A. Cellular responses to pathogen attack B. Environmental factors influencing resistance C. Genetic modification of plants D. Mechanisms of pathogen infection Answer: Cellular responses to pathogen attack (A) Gaümann focused on the hypersensitivity response in plants, which leads to cell death and isolation from pathogens. 43. In the study of plant diseases, which aspect was significantly advanced with Mills' research? A. Creating chemical treatments for pathogens B. Predicting infection risk based on environmental conditions C. Understanding pathogen life cycles D. Developing resistant plant varieties Answer: Predicting infection risk based on environmental conditions (B) Mills’ work allowed for the prediction of infection risk in apple plants based on rain and temperature. 44. Which of the following best describes systemic symptoms in plants? A. Symptoms that are limited to specific areas, such as spots. B. Symptoms solely visible on the vegetative structures. C. Symptoms that affect only the reproductive structures of the plant. D. Symptoms that manifest throughout the entire plant. Answer: Symptoms that manifest throughout the entire plant. (D) Systemic symptoms refer to generalized effects that can be observed throughout the plant, as opposed to localized symptoms. 45. What do plecionecrotic symptoms indicate in plant diseases? A. They indicate irreversible damage to plant tissues. B. They are symptoms that occur after the plant has died. C. They represent symptoms before the plant experiences cell death. D. They refer to external symptoms only. Answer: They represent symptoms before the plant experiences cell death. (C) Plecionecrotic symptoms are pre-necrotic, indicating changes in the plant prior to death. 46. What is a key component of Koch's postulates in proving pathogenicity? A. The same agent must be isolated from multiple infected plants. B. A symptom-free plant must show signs upon infection by the agent. C. The suspected agent must be isolated from healthy plants. D. The agent should only be present in young and healthy plants. Answer: The same agent must be isolated from multiple infected plants. (A) Koch's postulates require that the suspected causal agent is consistently found in all instances of the disease. 47. Which of the following is classified as a sign of plant diseases caused by viruses? A. Inclusion bodies B. Bacterial ooze C. Fruiting bodies D. Juvenile nematodes Answer: Inclusion bodies (A) Inclusion bodies are specific signs associated with viral plant diseases. 48. How is dry rot characterized in plant pathology? A. By excessive moisture leading to rapid decay. B. By a soft and mushy texture due to advanced decomposition. C. By firm and dry decay without moisture. D. By the presence of water-soaked tissue. Answer: By firm and dry decay without moisture. (C) Dry rot is defined as firm, dry decay, contrasting with soft rot which is associated with watery decomposition. 49. What was the significance of the discovery made by Woronin in 1878? A. He first observed myxomycetes related to clubroot disease of cabbage. B. He identified the cause of crown root gall in plants. C. He proved that toxins from fungi were responsible for cell death. D. He discovered a bacterium responsible for fire blight in apples. Answer: He first observed myxomycetes related to clubroot disease of cabbage. (A) Woronin was the first to observe myxomycetes, which cause clubroot disease in cabbage. 50. Which advancement in plant disease understanding occurred in the 1990s? A. Identification of the exact toxins produced by myxomycetes. B. Understanding the pathogens that cause soft rot. C. Discovery of the tobacco mosaic virus. D. Identification of systemic acquired resistance. Answer: Identification of systemic acquired resistance. (D) The 1990s saw significant discoveries related to systemic acquired resistance in plants. 51. Who was the first to demonstrate that fungi produce toxins, and in what year? A. deBary in 1886. B. L.R. Jones in 1905. C. Erwin Smith in 1905. D. A. Mayer in 1886. Answer: deBary in 1886. (A) deBary concluded in 1886 that fungi produce toxins that kill plant cells. 52. What was revealed about tobacco mosaic disease through the filtration experiments of Ivanowski in 1982? A. A virus was responsible for its causation. B. It is caused by fungal toxins. C. It was linked to a bacterial infection. D. It involves nutrient depletion in plants. Answer: A virus was responsible for its causation. (A) Ivanowski demonstrated that a virus, not bacteria, was the primary agent in tobacco mosaic disease. 53. Which agent did Erwin Smith identify as causing crown root gall? A. Agrobacterium tumefaciens. B. Various myxomycetes. C. Pseudomonas tabaci. D. Helminthosporium sp. Answer: Agrobacterium tumefaciens. (A) Erwin Smith discovered Agrobacterium tumefaciens as the causal agent of crown root gall. 54. In which year did Lafont discover protozoa in the cells of latex plants? A. 1931 B. 1926 C. 1909 D. 1947 Answer: 1909 (C) Lafont discovered protozoa in latex plants in 1909. 55. What significant finding was linked to the disease known as wildfire in 1934? A. Protozoans were found as the primary pathogen. B. The discovery of pectic enzymes. C. A new viral strain was identified. D. Toxins were confirmed to cause disease symptoms. Answer: Toxins were confirmed to cause disease symptoms. (D) In 1934, it was confirmed that toxins cause the symptoms associated with wildfire disease. 56. Which pathogen was confirmed to be involved in the white halo around spots of wildfire disease? A. Agrobacterium tumefaciens. B. Bipolaris sp. C. Pseudomonas tabaci. D. Helminthosporium sp. Answer: Pseudomonas tabaci. (C) The wildfire disease was caused by Pseudomonas tabaci, contributing to the white halo effect. 57. Which type of resistance is generally seen to be weaker but effective against all pathogen races? A. Adaptive resistance B. Genetic resistance C. Horizontal resistance D. Vertical resistance Answer: Horizontal resistance (C) Horizontal resistance is controlled by many minor resistance genes and is effective against all races of a pathogen species. 58. What is the primary mechanism through which plants achieve resistance according to E.Gaümann's 1946 proposal? A. Increased nutrient uptake B. Hypersensitivity leading to cell death C. Chemical barrier formation D. Structural changes in tissues Answer: Hypersensitivity leading to cell death (B) Hypersensitivity involves the immediate death of attacked and adjacent cells to isolate the pathogen. 59. What did Mills develop in 1944 to enhance predictions of plant infection? A. A method for soil analysis B. A table of rain duration and temperatures C. A disease resistance scale D. A new fungus variety Answer: A table of rain duration and temperatures (B) Mills created a table that linked the duration of rain to the infection of apple buds, leaves, and fruit. 60. Which term describes the control of plant disease through the production of phytoalexins? A. Systemic acquired resistance B. Induced resistance C. Constitutive resistance D. Chemical resistance Answer: Induced resistance (B) Phytoalexins are produced in response to pathogen attack, forming a part of induced resistance in plants. 61. What is a primary characteristic of vertical resistance in plants? A. Inherited in a polygenic manner B. Strong but effective against few races C. Effective against all pathogen species D. Controlled by multiple genes Answer: Strong but effective against few races (B) Vertical resistance is controlled by a few major resistance genes and is strong but effective only against one or few pathogen races. 62. What is the primary characteristic of biotrophs or obligate parasites? A. They can exist in nutrient media. B. They thrive on dead organic matter. C. They only reproduce in living hosts. D. They can live on both living and dead hosts. Answer: They only reproduce in living hosts. (C) Biotrophs or obligate parasites exclusively grow and reproduce in living hosts. 63. Which region was significantly affected by citrus canker, resulting in the eradication of millions of trees? A. Brazil B. Florida C. California D. Texas Answer: Florida (B) Citrus canker led to the eradication of millions of trees in Florida during the 1910s and again in the 1980s and 1990s. 64. The hypersensitive response in animals was later referred to as what? A. Defensive mechanism B. Necrosis C. Infarction D. Apoptosis Answer: Apoptosis (D) Apoptosis, meaning 'falling out', refers to the similar necrotic response seen in animals. 65. What does the study of plant pathology primarily focus on? A. Agricultural techniques for pest control B. Genetic modifications of crops C. Organisms and factors causing disease in plants D. Environmental impacts on climate Answer: Organisms and factors causing disease in plants (C) Plant pathology studies the organisms and environmental factors that cause diseases in plants. 66. During which decade were phytoalexins recognized to contribute to disease resistance in plants? A. 1940s B. 1930s C. 1960s D. 1970s Answer: 1960s (C) The study of phytoalexins in relation to disease resistance began in the 1960s. 67. What relationship is demonstrated by H.H. Flor's work with flax rust disease? A. Genetic variability does not affect infection rates. B. Resistance genes in hosts correspond to virulence genes in pathogens. C. Host plants require no genetic resistance. D. Every pathogen race can attack all host varieties. Answer: Resistance genes in hosts correspond to virulence genes in pathogens. (B) Flor established that each gene for resistance in the host corresponds with a gene for avirulence in the pathogen. 68. Which disease is known for causing severe losses by killing numerous trees annually in North America and Europe? A. Apple scab B. Citrus canker C. Southern blight D. Fire blight of pome fruits Answer: Fire blight of pome fruits (D) Fire blight of pome fruits is known to kill numerous trees annually in North America and Europe. 69. What term best describes pathogens that can live on either living or dead hosts? A. Nonobligate parasites B. Necrotrophs C. Facultative saprophytes D. Biotrophs Answer: Nonobligate parasites (A) Nonobligate parasites can live on both living and dead hosts as well as on various nutrient media. 70. What study method did Mills and others utilize to predict infection by apple scab? A. Microbial analysis B. Statistical modeling C. Time-lapse imaging D. Environmental correlation Answer: Environmental correlation (D) Mills developed a method of correlating the duration of rain required at different temperatures to predict infection. 71. Which of the following concepts differentiates disease endurance from disease resistance? A. Endurance focuses on surviving after infection. B. Endurance results from genetic factors. C. Endurance leads to necrosis of host tissues. D. Endurance means the plant can escape infection. Answer: Endurance focuses on surviving after infection. (A) Disease endurance (tolerance) reflects the plant's ability to survive and function despite infection. 72. What is a defining feature of facultative parasites? A. They only infect living plants. B. They require a specific host to reproduce. C. They primarily thrive on dead organic matter. D. They can shift to saprophytic growth when conditions are suitable. Answer: They can shift to saprophytic growth when conditions are suitable. (D) Facultative parasites can act as necrotrophs, thriving on dead matter when conditions allow. 73. Who contributed to the understanding of genetic variability within a pathogen species? A. Klement B. Stakman C. Barrus D. Biffen Answer: Barrus (C) Barrus showed that different pathogen races could be restricted to specific host varieties. 74. What is the primary implication of the gene-for-gene relationship established by H.H. Flor? A. Host plants cannot develop resistance without external forces. B. Pathogen genes are irrelevant to host resistance. C. Virulence and susceptibility are unlinked. D. Every resistance gene is matched with a virulence gene in pathogens. Answer: Every resistance gene is matched with a virulence gene in pathogens. (D) Flor's work illustrated that for every host resistance gene, there is a corresponding gene for virulence in pathogens. 75. Which of the following accurately describes semi-biotrophs or facultative saprophytes? A. They can only grow as parasites. B. They mostly live parasitically but can grow saprophytically under certain conditions. C. They are typically limited to nutrient media. D. They thrive solely on living hosts. Answer: They mostly live parasitically but can grow saprophytically under certain conditions. (B) Semi-biotrophs or facultative saprophytes primarily behave as parasites but can adopt saprophytic growth if conditions permit. 76. What concept refers to the resistance inherited from one or both parent wheat varieties to a rust fungus? A. Hypersensitive response B. Tolerance C. Inherited Resistance D. Nonobligate resistance Answer: Inherited Resistance (C) Inherited Resistance refers to the genetic passing of resistance traits from parent to progeny. 77. What condition is characterized by the yellowing of plant leaves not caused by light deficiency? A. Damping off B. Chlorosis C. Etiolation D. Curling Answer: Chlorosis (B) Chlorosis refers to the yellowing of leaves that occurs due to various factors excluding light. 78. Which term describes the drying backward from the tip of a plant? A. Scab B. Blight C. Die-back D. Canker Answer: Die-back (C) Die-back is a symptom where the plant dries out starting from the tip. 79. What type of abnormal plant tissue growth is formed due to injury? A. Canker B. Callus C. Blotch D. Savoying Answer: Callus (B) Callus tissue is an overgrowth that forms as a response to injury in plants. 80. What is the term for extensive sudden death of host tissues caused by a pathogen? A. Spot B. Damping off C. Blight D. Etiolation Answer: Blight (C) Blight is characterized by rapid and widespread death of plant tissues. 81. What symptom is described by large, irregular spots on leaves or fruits due to necrotic injury? A. Chlorosis B. Blotch C. Scab D. Canker Answer: Blotch (B) Blotch refers to the appearance of large, irregular spots resulting from necrotic tissue damage. 82. Which term refers to the localized necrotic area also known as a lesion? A. Spot B. Savoying C. Bleeding D. Curling Answer: Spot (A) Spot is a term that identifies localized areas of necrotic injury in plants. 83. What phenomenon leads to the rotting of seedlings prior to emergence? A. Damping off B. Die-back C. Blight D. Curling Answer: Damping off (A) Damping off is a common issue that results in seedling rot before they can emerge. 84. Which symptom is characterized by the formation of slightly raised, rough, ulcer-like lesions? A. Blotchy B. Savoying C. Canker D. Scab Answer: Scab (D) Scab presents as raised lesions that can vary in texture and appearance on plant surfaces. 85. What symptom involves the cupping or pocketing of parts of a leaf? A. Savoying B. Bleeding C. Curling D. Chlorosis Answer: Savoying (A) Savoying refers to abnormal leaf shapes characterized by cupping and protrusions. 86. What term describes long, narrow necrotic lesions on leaves or stems? A. Blotchy B. Spot C. Blight D. Streak or stripe Answer: Streak or stripe (D) Streak or stripe refers to the linear pattern of necrosis appearing on plant tissues. 87. Who established the germ theory of disease? A. Alexander Fleming B. Charles Darwin C. Louis Pasteur D. Robert Petri Answer: Louis Pasteur (C) Louis Pasteur's work led to the establishment of the germ theory, which proposed that many diseases are caused by microorganisms. 88. What was the first dithiocarbamate fungicide developed? A. Streptomycin B. Carboxin C. Penicillin D. Thiram Answer: Thiram (D) Thiram, developed in 1934, was the first dithiocarbamate fungicide used for agricultural purposes. 89. What significant advancement occurred in 1965 in the field of fungicides? A. Discovery of penicillin B. Development of systemic fungicides C. Widespread use of antibiotics D. Isolation of smut spores Answer: Development of systemic fungicides (B) In 1965, carboxin marked the introduction of the first systemic fungicide to control plant pathogens. 90. Which scientist proved that potato late blight was caused by a fungus? A. Pier Antonio Micheli B. Anton deBary C. Needham D. Kühn Answer: Anton deBary (B) Anton deBary's research in 1861-1863 established the fungal cause of potato late blight. 91. Which of the following provided evidence against spontaneous generation? A. Charles Darwin B. Louis Pasteur C. Robert Petri D. Needham Answer: Louis Pasteur (B) Louis Pasteur's experiments demonstrated that microorganisms arise from existing microbes, challenging the concept of spontaneous generation. 92. What was the primary focus of Kühn's book published in the 1870s? A. Diseases of cultivated crops B. Microbial resistance in crops C. Evolution of plant pathogens D. Chemical treatments for plant diseases Answer: Diseases of cultivated crops (A) Kühn's book, 'Diseases of Cultivated Crops', addressed the various causes of plant diseases and laid the groundwork for plant pathology. 93. What was the primary finding of research conducted in the 1970s related to fungicides? A. Fungicides began to fail due to increased costs B. Pathogen races showed increased resistance to fungicides C. Fungicide applications were banned worldwide D. The emergence of viral diseases in crops Answer: Pathogen races showed increased resistance to fungicides (B) The widespread use of systemic fungicides in the 1970s led to the emergence of many resistant fungal strains. 94. Which antibiotic was primarily used against bacteria in 1950? A. Thiram B. Carboxin C. Streptomycin D. Tetracycline Answer: Streptomycin (C) Streptomycin was prominently used as an antibiotic against bacterial infections starting in 1950. 95. What symptom is associated with the gumming or exudation of viscid gum from wounds in bark? A. Mottling B. Mummification C. Mosaic D. Gumming/gummosis Answer: Gumming/gummosis (D) Gumming or gummosis occurs when viscid gum seeps out from damaged bark. 96. What condition is primarily characterized by the oozing out of juices from soft, rotted portions of a plant? A. Leak B. Wilting C. Phyllody D. Pitting Answer: Leak (A) Leak refers to the exudation of juices from areas of decay in plant tissues. 97. Which term refers to the phenomenon where the leaf veins appear pale while the surrounding leaf tissue remains normal? A. Wilting B. Virescence C. Vein clearing D. Rosetting Answer: Vein clearing (C) Vein clearing is identified by translucent or pale veins contrasting with normal leaf color. 98. Mosaic symptoms in plants are identified by what specific characteristic? A. Crowding of foliage B. Pockmarked surface appearance C. Lack of chlorophyll D. Defined variegated patterns Answer: Defined variegated patterns (D) Mosaic symptoms manifest as variegated patterns with clearly defined borders. 99. What does the term 'mummification' refer to in plant diseases? A. Browning of leaf edges B. Chlorophyll development in abnormal areas C. Loss of leaf turgor D. Shriveling of infected tissue Answer: Shriveling of infected tissue (D) Mummification describes the process where infected fruits shrivel up and take on a dried appearance. 100. What is the total annual economic loss attributed to plant diseases worldwide? A. $220 billion B. $420 billion C. $120 billion D. $320 billion Answer: $220 billion (A) The total annual crop loss from plant diseases is estimated to be about $220 billion. 101. Which disease resulted in the historical loss of 10 million peach trees? A. Pear decline B. Root knot C. Peach yellows D. Cereal rusts Answer: Peach yellows (C) The disease called Peach yellows caused significant historical losses in the Eastern U.S. and Russia. 102. What type of losses are associated with nematode diseases? A. Improvement of soil health B. Reduced pest resistance C. Instantaneous total crop failure D. Continuous losses on vegetables and other plants Answer: Continuous losses on vegetables and other plants (D) Nematode diseases are known to cause continuous losses on vegetables and most other plants. 103. Which plant disease is identified as causing severe annual losses on sugar beets in Northern Europe? A. Peach yellows B. Sugar beet cyst nematode C. Cereal rusts D. Soybean cyst nematode Answer: Sugar beet cyst nematode (B) The sugar beet cyst nematode is noted for causing continuous severe annual losses on sugar beets. 104. What is a primary objective of plant pathology? A. To enhance soil fertility B. To promote pest proliferation C. To cultivate new plant species D. To prevent and minimize plant diseases Answer: To prevent and minimize plant diseases (D) The main goal of plant pathology is to prevent and minimize plant diseases to increase food production and quality. 105. Which nematode disease is associated with continuous serious losses on soybeans in Asia and North & South America? A. Peach yellows B. Sugar beet cyst nematode C. Root knot D. Soybean cyst nematode Answer: Soybean cyst nematode (D) The soybean cyst nematode is linked to continuous serious losses on soybeans in various regions. 106. What percentage of crops are estimated to be lost to plant diseases? A. 14.1% B. 20.3% C. 5.2% D. 10.1% Answer: 14.1% (A) It is estimated that 14.1% of crops are lost to plant diseases. 107. Which of the following diseases is widely known for causing frequent severe epidemics globally? A. Root knot B. Peach yellows C. Soybean cyst nematode D. Cereal rusts Answer: Cereal rusts (D) Cereal rusts are known for triggering frequent severe epidemics, leading to large annual losses. 108. What is a significant economic impact of plant diseases mentioned? A. Losses of approximately $220 billion B. Increased food prices C. Complete crop destruction D. Reduction in plant breeding efforts Answer: Losses of approximately $220 billion (A) The economic impact of plant diseases is substantial, with annual losses amounting to around $220 billion. 109. Which disease is highlighted for killing millions of pear trees across multiple regions? A. Sugar beet cyst nematode B. Peach yellows C. Pear decline D. Root knot Answer: Pear decline (C) Pear decline has led to the killing of millions of pear trees, particularly noted in the Pacific coast states and Canada. 110. What describes nonobligate parasites in relation to their hosts? A. They thrive exclusively on dead organic matter. B. They can only live on living hosts. C. They can live on either living or dead hosts. D. They require living hosts for reproduction. Answer: They can live on either living or dead hosts. (C) Nonobligate parasites can thrive on various nutrient media, including both living and dead hosts. 111. The term 'hypersensitive response' in plants is characterized by which of the following actions? A. A necrotic defense reaction to isolate pathogens. B. Selective accumulation of nutrients. C. Immediate growth promotion of surrounding tissues. D. Enhancement of photosynthesis in infected areas. Answer: A necrotic defense reaction to isolate pathogens. (A) The hypersensitive response involves immediate cell death to prevent the spread of pathogens. 112. What relationship was established by H.H. Flor in regard to resistance in plants? A. Genetic variability in pathogens does not influence host defense mechanisms. B. Pathogen virulence does not affect host susceptibility. C. Resistance is determined solely by environmental factors. D. For each resistance gene in the host, there exists a corresponding gene for avirulence in the pathogen. Answer: For each resistance gene in the host, there exists a corresponding gene for avirulence in the pathogen. (D) Flor's research pointed to a gene-for-gene relationship between hosts and pathogens. 113. What distinguishes semi-biotrophs from other parasite types? A. They can only thrive on living hosts. B. They live primarily on dead organic matter. C. They are obligate parasites that cannot survive without a host. D. They can act either as parasites or saprophytes under certain conditions. Answer: They can act either as parasites or saprophytes under certain conditions. (D) Semi-biotrophs can switch between a parasitic and saprophytic lifestyle based on environmental conditions. 114. In context to plant resistance studies, Biffen's observations regarding wheat varieties introduced the concept of what? A. Gene therapy for crop improvement. B. Sustainable agricultural practices. C. Acquired immunity. D. Mendelian inheritance of resistance traits. Answer: Mendelian inheritance of resistance traits. (D) Biffen's reports highlighted the inherited nature of resistance against rust fungi in wheat. 115. Which term refers to the genetic variability within a pathogen species that affects its ability to attack host plants? A. Phenotypic plasticity. B. Mendelian inheritance. C. Pathogen races. D. Genetic drift. Answer: Pathogen races. (C) Orton's work emphasized that genetic variability leads to different pathogen races affecting specific varieties of host species. 116. Which of the following statements is true regarding necrotrophs? A. They do not reproduce in the absence of living hosts. B. They live exclusively as saprophytes. C. They thrive on both dead organic matter and living hosts, especially when they become parasitic. D. They primarily target living plants for sustenance. Answer: They thrive on both dead organic matter and living hosts, especially when they become parasitic. (C) Necrotrophs can effectively exploit both live and decaying organic matter for their lifecycle. 117. Which aspect of plant disease resistance was assessed by Orton's research on Fusarium wilts? A. The relationship between plant size and resistance levels. B. The effects of temperature variations on pathogen virulence. C. The distinctions among disease resistance, disease escape, and disease endurance. D. The balance of nutrient availability and disease resistance. Answer: The distinctions among disease resistance, disease escape, and disease endurance. (C) Orton's work helped clarify different mechanisms that contribute to how plants interact with pathogens. 118. What characteristic defines obligate biotrophs? A. They can thrive on dead organic matter. B. They are facultative parasites depending on environmental conditions. C. They can be grown in vitro on artificial media. D. They require living hosts for their complete lifecycle. Answer: They require living hosts for their complete lifecycle. (D) Obligate biotrophs rely exclusively on living hosts for growth and reproduction. 119. Which year did Z. Klement and colleagues recognize the hypersensitive response as a defense mechanism against bacterial plant pathogens? A. 1964 B. 1972 C. 1914 D. 1905 Answer: 1964 (A) The recognition of the hypersensitive response as a defense against bacterial pathogens was made in 1964. 120. What economic impact did the Southern corn leaf blight have in the U.S. during its epidemic? A. $750 million lost B. $2 billion lost C. $1 billion lost D. $500 million lost Answer: $1 billion lost (C) The epidemic of Southern corn leaf blight in 1970 resulted in significant economic losses estimated at $1 billion. 121. Which disease was primarily responsible for the Irish famine in the 1845–46 period? A. Chestnut blight B. Ergot of rye C. Late blight of potato D. Brown spot of rice Answer: Late blight of potato (C) The late blight of potato caused annual epidemics, contributing significantly to the Irish famine. 122. What type of toxin is produced by A. flavus in corn and sorghum? A. Ochratoxin B. Estrogenic factor C. Aflatoxin D. Yellow rice toxin Answer: Aflatoxin (C) Aflatoxin, produced by A. flavus, is noted for its carcinogenic properties. 123. Which disease had a significant impact on the quality of produce during epidemics in Asia, particularly during the Bengal famine of 1943? A. Downy mildew of corn B. Brown spot of rice C. Powdery mildew of grapes D. Chestnut blight Answer: Brown spot of rice (B) The brown spot of rice was associated with significant reductions in the quality of rice during the Bengal famine. 124. What is the primary region affected by the brown spot of rice? A. Europe B. Africa C. U.S. D. Asia Answer: Asia (D) The brown spot of rice is primarily an epidemic disease affecting Asia. 125. What was the main consequence of the chestnut blight in the U.S. from 1904 to 1940? A. Loss of all American chestnut trees B. Increase in soil erosion C. Destruction of fruit crops D. Reduction in oak tree populations Answer: Loss of all American chestnut trees (A) The chestnut blight led to the destruction of almost all American chestnut trees in that period. 126. Which pathogen is responsible for the disease known as late blight? A. A. flavus B. C. purpurea C. P. infestans D. Fusarium graminearum Answer: P. infestans (C) Late blight of potato is caused by the pathogen Phytophthora infestans. 127. What kind of economic damage does downy mildew of corn cause annually in the Philippines? A. P170 million B. P100 million C. P50 million D. P250 million Answer: P170 million (A) Downy mildew of corn results in significant losses, amounting to over P170 million annually in the Philippines. 128. Which type of toxin associated with downy mildew of tobacco is known for causing cancer of the liver? A. Ochratoxin B. Yellow rice toxins C. Aflatoxin D. Estrogenic factor Answer: Ochratoxin (A) Ochratoxin, produced by A. ochraceus, is associated with the downy mildew of tobacco and is known to cause liver cancer. 129. What kind of losses do cereal smuts cause globally? A. Total crop failure B. Increased soil fertility C. Severe financial distress to farmers D. Continuous, although lesser, losses on all grains Answer: Continuous, although lesser, losses on all grains (D) Cereal smuts lead to continuous, albeit lesser, losses on all grains globally. 130. What is indicated by the development of chlorophyll in tissues or organs where it is normally absent? A. Gumming B. Virescence C. Mummification D. Mottling Answer: Virescence (B) Virescence refers to the unusual development of chlorophyll in plant tissues. 131. Which symptom is characterized by extreme clustering of plant parts around a common focus? A. Rosetting B. Mosaic C. Pitting D. Fasciculation Answer: Fasciculation (D) Fasciculation describes the clustering of roots, flowers, fruits, or twigs. 132. What condition results in the crinkling and crowding of foliage in a rosette pattern? A. Leak B. Rosetting C. Wilting D. Phyllody Answer: Rosetting (B) Rosetting is defined by the crowding of foliage into a rosette shape. 133. Which symptom is related to the leaf veins showing translucency or a pale while other parts remain normal? A. Flecks B. Mottling C. Vein clearing D. Gumming Answer: Vein clearing (C) Vein clearing involves the leaf veins becoming translucent or pale compared to the rest of the leaf. 134. What symptom involves tiny spots, often extremely small, appearing on leaves and other plant parts? A. Vein clearing B. Pitting C. Flecks D. Gumming Answer: Flecks (C) Flecks are characterized by extremely tiny spots appearing on various parts of plants. 135. Which scientist is known for establishing binomial nomenclature of plants? A. Theophrastus B. Robert Hooke C. Antonius van Leeuwenhoek D. Carl von Linne Answer: Carl von Linne (D) Carl von Linne published 'Systema Naturae' in 1735, which established the system of binomial nomenclature for naming plants. 136. What discovery is attributed to Robert Hooke? A. Identification of plant pathogens B. Development of chemical control methods C. Invention of the compound microscope D. Discovery of microorganisms Answer: Invention of the compound microscope (C) Robert Hooke invented the compound microscope and discovered the structure of the cell, marking a significant advancement in biology. 137. Which phase in the development of plant pathology focused on proving the causes of plant diseases? A. Descriptive Phase B. Experimental Phase C. Biological Phase D. Etiological Phase Answer: Etiological Phase (D) The Etiological Phase was crucial for establishing the causes of plant diseases through scientific investigations. 138. What mixture did Millardet invent in 1885 that contributed to plant disease control? A. Sulfur solution B. Bordeaux mixture C. Mercuric chloride D. Copper oxychloride Answer: Bordeaux mixture (B) Millardet invented the Bordeaux mixture, a key development in the chemical control of plant diseases. 139. Who recognized mistletoe as the first plant pathogen? A. Theophrastus B. Carl von Linne C. Antonius van Leeuwenhoek D. Albertus Magnus Answer: Albertus Magnus (D) Albertus Magnus identified mistletoe as the first known plant pathogen, highlighting early understanding of plant diseases. 140. Which of the following describes Theophrastus's belief about plant diseases? A. Diseases were caused by environmental factors B. Diseases arose spontaneously from the soil C. Diseases were transmitted by bacteria D. Diseases resulted from God's wrath Answer: Diseases resulted from God's wrath (D) Theophrastus, considered the father of botany, believed that diseases in plants were manifestations of divine discontent. 141. What was the main focus of the Descriptive Phase in plant pathology? A. Identification of pathogenic organisms B. Designing experiments for disease testing C. Studying plant responses to pathogens D. Discovery and development of growth methodologies Answer: Discovery and development of growth methodologies (D) The Descriptive Phase focused primarily on the discovery and development of methodologies for studying and growing microbes. 142. Which event is associated with Thoullier in relation to plant diseases? A. Discovery of ergotism and its spread B. The invention of Bordeaux mixture C. First use of the microscope D. Identification of plant cellular structures Answer: Discovery of ergotism and its spread (A) Thoullier observed ergotism, known as Holy Fire, and determined that it spread through the consumption of infected wheat. 143. What was the significance of Louis Pasteur's work in the context of plant pathology? A. He discovered the first systemic fungicide. B. He described the nematodes for the first time. C. He created artificial nutrient media. D. He established the germ theory of disease. Answer: He established the germ theory of disease. (D) Louis Pasteur proved that most infectious diseases were caused by germs. 144. Which compound was first identified as a dithiocarbamate fungicide in 1934? A. Penicillin B. Streptomycin C. Carboxin D. Thiram Answer: Thiram (D) Thiram was the first dithiocarbamate fungicide developed. 145. What did Anton deBary prove regarding potato late blight? A. It was caused by a fungus. B. It was a bacterial infection. C. It was caused by a virus. D. It resulted from environmental conditions. Answer: It was caused by a fungus. (A) Anton deBary proved that potato late blight was caused by a fungus. 146. What advancement in fungicide development occurred in 1965? A. The development of the first systemic fungicide. B. The creation of artificial nutrient media. C. The discovery of penicillin. D. The introduction of antibiotics for bacterial control. Answer: The development of the first systemic fungicide. (A) 1965 saw the introduction of the first systemic fungicide, carboxin. 147. What was one of the early observations made by Needham regarding nematodes? A. He first observed nematodes in 1743. B. He was the first to describe their life cycle. C. He noted their role in plant diseases. D. He discovered treatments for their control. Answer: He first observed nematodes in 1743. (A) Needham was the first to observe nematodes in 1743. 148. What did the widespread use of systemic fungicides in the 1970s lead to? A. The discovery of new fungicide compounds. B. An eradication of plant pathogens. C. The appearance of resistant fungal strains. D. Increased crop yields significantly. Answer: The appearance of resistant fungal strains. (C) The widespread use of systemic fungicides caused the appearance of many resistant fungi. 149. Which disease was responsible for significant losses in peach trees during the 1910s? A. Potato late blight. B. Peach bacterial spot. C. Peach root rot. D. Tobacco mosaic disease. Answer: Peach root rot. (C) The disease caused the death of millions of peach trees in the Eastern U.S. during the 1910s. 150. What was Charles Darwin's major publication focused on? A. The role of fungi in diseases. B. The origin of species by means of natural selection. C. The importance of antibiotics. D. Plant disease resistance mechanisms. Answer: The origin of species by means of natural selection. (B) Charles Darwin published 'The Origin of Species by Means of Natural Selection' in 1859. 151. What did Robert Petri contribute to microbiology? A. The identification of smut spores. B. The development of antibiotics. C. The creation of artificial nutrient media. D. The discovery of systemic fungicides. Answer: The creation of artificial nutrient media. (C) Robert Petri developed artificial nutrient media for culture of microorganisms. 152. What was a primary finding of Prevost regarding smut disease? A. It is caused by a nematode. B. It can be treated with antibiotics. C. Smut spores gave rise to smut disease. D. Fungi are not responsible for plant diseases. Answer: Smut spores gave rise to smut disease. (C) Prevost concluded that smut spores gave rise to smut disease in 1807. 153. What discovery did Erwin Smith make regarding a specific bacteria related to plant diseases? A. It was the first commercial synthesized plant defense activator. B. It induced systemic acquired resistance. C. It caused crown root gall in plants. D. It caused clubroot disease of cabbage. Answer: It caused crown root gall in plants. (C) Erwin Smith discovered Agrobacterium tumefaciens as the causal agent of crown root gall. 154. What specific disease caused significant destruction of coffee in Southeast Asia during the late 19th century? A. Dwarf mistletoes B. Pine stem rusts C. Coffee rust D. Citrus tristeza Answer: Coffee rust (C) Coffee rust was particularly devastating in Southeast Asia during the 1870s and 1880s. 155. Which enzymatic activity was reported to be involved in soft rot of vegetables? A. Toxic enzymes B. Cytolytic enzymes C. Pectic enzymes D. Starch degrading enzymes Answer: Cytolytic enzymes (B) In 1905, L.R. Jones reported the involvement of cytolytic enzymes in soft rot of vegetables. 156. What significant role did viruses play in plant disease as demonstrated by deBary's conclusion? A. Produced toxins that kill plant cells. B. Induce hypersensitive responses in plants. C. Interfere with photosynthesis in host plants. D. Act as vectors for bacterial infections. Answer: Produced toxins that kill plant cells. (A) DeBary concluded that fungi produce toxins that kill cells in advance, showing a significant role in plant diseases. 157. Which pathogen is linked to severe losses of rubber tree plantations in South America? A. Fusarium spp. B. Fusarium scab C. M.fijiensis D. Armillaria mellea Answer: Armillaria mellea (D) Rubber leaf blight results in destruction of rubber tree plantations, making them vulnerable to Armillaria mellea. 158. Which organism was shown to cause coffee diseases in 1963? A. Pseudomonas tabaci B. Protozoans C. Phytophthora D. Bipolaris sp. Answer: Protozoans (B) Vermeulen proved that protozoans caused disease in coffee in 1963. 159. Which disease is responsible for the serious loss of American elm trees since 1918? A. Sugar beet yellows B. Swollen shoot of cacao C. Citrus tristeza D. Dutch elm disease Answer: Dutch elm disease (D) Dutch elm disease has caused considerable destruction of American elm trees over the last century. 160. Which technological advancement in the late 1980s focused on plant disease resistance? A. Traditional breeding techniques B. Genetic engineering C. Biological control methods D. Chemical pest control Answer: Genetic engineering (B) The late 1980s saw the use of genetic engineering to induce resistance to plant diseases. 161. What type of losses do leaf pathogens like M.fijiensis primarily lead to? A. Defoliation and weakening of plants B. Plant virus spread C. Esophageal cancer in humans D. Root-rotting diseases Answer: Defoliation and weakening of plants (A) Leaf pathogens weaken plants, which can lead to susceptibility to root-rotting pathogens. 162. What was revealed about the tobacco mosaic virus in 1898 by Beijerinck? A. It primarily affected root systems. B. It produced lethal toxins. C. It was caused by a contagious living fluid. D. It was the first DNA virus discovered. Answer: It was caused by a contagious living fluid. (C) Beijerinck discovered that the tobacco mosaic was caused by a 'contagious living fluid' called virus. 163. Which pathogen has caused continuous heavy losses in cacao, notably in Africa? A. Citrus tristeza B. Swollen shoot of cacao C. Sugar cane mosaic D. Fusarium scab of wheat Answer: Swollen shoot of cacao (B) The swollen shoot of cacao results in ongoing losses in African regions. 164. What was a major consequence of sugar cane mosaic in agricultural production? A. Enhanced disease resistance B. Increased sugar quality C. Reduced handling costs D. Great losses on sugar cane and corn Answer: Great losses on sugar cane and corn (D) Sugar cane mosaic has resulted in substantial agricultural losses on both sugar cane and corn crops. 165. Which pathogen is associated with the white halo around spots of wildfire disease? A. Agrobacterium tumefaciens B. Helminthosporium sp. C. Pseudomonas tabaci D. Pseudomonas syringae Answer: Pseudomonas tabaci (C) Wildfire disease is caused by Pseudomonas tabaci, confirmed with toxin involvement. 166. What did A. Mayer demonstrate regarding plant diseases in 1886? A. Transmission methods of tobacco diseases. B. Effects of viral infections on root growth. C. The role of fungi in virulence. D. Pathogenicity of leaf juices with yellow mosaic. Answer: Pathogenicity of leaf juices with yellow mosaic. (D) A. Mayer demonstrated the pathogenicity of leaf juices of tobacco with yellow mosaic in 1886. 167. Which disease is known to significantly weaken crops and predispose them to attacks by other pathogens? A. Coffee rust B. Banana leaf spot C. Fusarium scab of wheat D. Dwarf mistletoes Answer: Coffee rust (A) Coffee rust compromises plant health, making them more susceptible to other pathogens. 168. What was the significant finding about mollicutes in 1926 by E. Kurosawa? A. They were associated with major crop failures. B. They caused root galls in apples. C. They produced toxins detrimental to plant health. D. They resulted in excessive growth in infected rice seedlings. Answer: They resulted in excessive growth in infected rice seedlings. (D) E. Kurosawa showed that the excessive growth of rice seedlings was infected with mollicutes. 169. Which disease has notably affected the sugar beet crop in Northern Europe and the Western U.S.? A. Citrus tristeza B. Sugar beet yellows C. Pine stem rusts D. Fusarium scab of wheat Answer: Sugar beet yellows (B) Sugar beet yellows is known for causing severe annual losses in sugar beet crops. 170. What significant agricultural loss is attributed to banana leaf spot or Sigatoka? A. Great annual losses in banana cultivation B. Loss of coffee production C. Destruction of elm trees D. Severe damage to rubber plantations Answer: Great annual losses in banana cultivation (A) Banana leaf spot leads to substantial annual losses in banana agriculture. 171. Which advancement in plant disease understanding occurred during the 1990s? A. Discovery of viral resistance genes. B. Improvement of chemical fungicides. C. Establishment of integrated pest management. D. Development of systemic acquired resistance. Answer: Development of systemic acquired resistance. (D) The 1990s saw the discovery of systemic acquired (or induced or activated) resistance. 172. What phenomenon is caused by fungal infections such as Fusarium spp. in corn grains? A. Defoliation B. Esophageal cancer C. Crop yield increase D. Root rot Answer: Esophageal cancer (B) Fumonisins produced by Fusarium spp. in corn grains have been linked to human esophageal cancer. 173. What was the primary belief about plant diseases held by Theophrastus? A. They were manifestations of God's wrath. B. They were a result of human negligence. C. They were caused by natural decomposition processes. D. They could be controlled through agricultural practices. Answer: They were manifestations of God's wrath. (A) Theophrastus viewed plant diseases as a result of divine punishment. 174. Which significant contribution did Robert Hooke make to plant pathology? A. Invention of the microscope. B. Establishment of binomial nomenclature. C. Discovery of microorganisms. D. Identification of specific plant pathogens. Answer: Invention of the microscope. (A) Robert Hooke invented the compound microscope, which was essential for studying plant diseases. 175. Who is credited with improving the microscope and discovering microorganisms? A. Antonius van Leeuwenhoek B. Theophrastus C. Carl von Linne D. Robert Hooke Answer: Antonius van Leeuwenhoek (A) Antonius van Leeuwenhoek significantly advanced microscopy and discovered microorganisms. 176. What phase of plant pathology focuses on proving the causes of plant diseases? A. Descriptive Phase B. Etiological Phase C. Chemical Control Phase D. Experimental Phase Answer: Etiological Phase (B) The Etiological Phase is concerned with identifying and proving the causes of plant diseases. 177. What was the primary discovery associated with Millardet in the context of controlling plant diseases? A. Invention of the Bordeaux mixture. B. Discovery of a new plant pathogen. C. Identification of the first viral plant disease. D. Development of organic farming methods. Answer: Invention of the Bordeaux mixture. (A) Millardet invented the Bordeaux mixture, a significant chemical control for plant diseases. 178. Which holiday celebrated the rust god Robigus in ancient Rome? A. Floralia B. Lupercalia C. Robigalia D. Saturnalia Answer: Robigalia (C) Robigalia was a holiday dedicated to Robigus, the rust god, aimed at protecting crops from rust diseases. 179. What significant aspect of plant pathology began its Descriptive Phase? A. Identification of plant pathogens. B. Studies on microbial growth. C. Testing plant response to diseases. D. Design of chemical controls. Answer: Identification of plant pathogens. (A) The Descriptive Phase involved discovering and developing methodologies for studying and identifying pathogens. 180. In which year was the concept of binomial nomenclature established? A. 1735 B. 1885 C. 1670 D. 1944 Answer: 1735 (A) Carl von Linne published 'Systema Naturae' in 1735, which established the binomial nomenclature of plants. 181. What is Sarcody in plant pathology? A. The yellowing of leaves due to reduced light B. The drying backward of plant parts C. The sudden death of host tissues D. The abnormal swelling of the bark above an injury Answer: The abnormal swelling of the bark above an injury (D) Sarcody is described as an abnormal swelling of the bark above an injury. 182. Which term describes sunken necrotic areas with cracked borders? A. Scab B. Callus C. Canker D. Blight Answer: Canker (C) Canker is defined as a sunken necrotic area with a cracked border. 183. What does chlorosis indicate in plant tissues? A. Large, irregular spots on leaves B. Underdevelopment of leaf veins C. Abnormal swelling in bark D. Yellowing not caused by light deficiency Answer: Yellowing not caused by light deficiency (D) Chlorosis refers to the yellowing of plant leaves not caused by light deficiency. 184. What type of plant disease symptom is characterized by curled leaves? A. Die-back B. Curling C. Damping off D. Canker Answer: Curling (B) Curling is defined as the abnormal bending or curling of leaves. 185. What does the term 'blight' refer to in plant pathology? A. Yellowing of leaves due to inadequate light B. Extensive sudden death of host tissues C. Localized necrotic areas on leaves D. Slowed growth due to nutrient deficiency Answer: Extensive sudden death of host tissues (B) Blight is described as an extensive sudden death of host tissues. 186. What is the term used to describe parasites that can thrive on both living hosts and dead organic matter? A. Biotrophs B. Obligate parasites C. Necrotrophs D. Facultative parasites Answer: Facultative parasites (D) Facultative parasites can feed on both living and dead matter, while obligate parasites require living hosts. 187. Which response is characterized by the immediate death of cells surrounding an invading pathogen? A. Necrosis B. Hypersensitive response C. Apoptosis D. Disease tolerance Answer: Hypersensitive response (B) The hypersensitive response isolates the pathogen by causing immediate cell death in the affected area. 188. What do we call the genetic variability within a pathogen species that affects its ability to infect different hosts? A. Pathogen races B. Host resistance C. Gene-for-gene relationship D. Diseases escape Answer: Pathogen races (A) Pathogen races exhibit differences in their ability to attack specific varieties of host plants. 189. Which term describes the interaction where there is a specific gene in the host for resistance matched by a gene for avirulence in the pathogen? A. Independent action B. Gene-for-gene relationship C. Facultative relationship D. Hypersensitive response Answer: Gene-for-gene relationship (B) The gene-for-gene relationship is critical in understanding plant-pathogen interactions and resistance mechanisms. 190. What type of parasite primarily relies on living organisms for its nutritional needs? A. Saprophytes B. Biotrophs C. Necrotrophs D. Facultative saprophytes Answer: Biotrophs (B) Biotrophs or obligate parasites grow and reproduce only in living hosts, creating a symbiotic relationship. 191. Which type of research differentiates between disease resistance, escape, and endurance? A. Biffen's study B. Barrus' research C. Stakman's analysis D. Klement's observation Answer: Barrus' research (B) Barrus' work in 1909 established a framework for understanding different strategies of plant defenses against diseases. 192. What does the term 'apoptosis' refer to in the context of plant responses? A. Programmed cell death B. Pathogen resistance C. Cell division D. Nutrient uptake Answer: Programmed cell death (A) Apoptosis describes a necessary programmed cell death which plays a role in the plant's defense mechanism against pathogens. 193. Which of the following correctly describes semi-biotrophs or facultative saprophytes? A. Primarily live as parasites, but can also grow on dead matter B. Only thrive on living hosts C. Always require specific genetic traits from hosts D. Only thrive on dead organic matter Answer: Primarily live as parasites, but can also grow on dead matter (A) Semi-biotrophs or facultative saprophytes can shift between being parasitic or saprophytic based on conditions. 194. Which scientist established the concept of host genetic resistance corresponding to pathogen genetic avirulence? A. Barrus B. Z. Klement C. Biffen D. H.H. Flor Answer: H.H. Flor (D) H.H. Flor's research pioneered the understanding of the genetic interactions between hosts and pathogens. 195. What was identified by Orton regarding plant diseases? A. The gene-for-gene relationship B. Distinction between resistance, escape, and endurance C. Resistance mechanisms D. The role of necrosis Answer: Distinction between resistance, escape, and endurance (B) Orton's work in 1909 was significant for distinguishing between various forms of plant responses to disease. 196. What is the primary characteristic of horizontal resistance in plants? A. Weak but effective against all races of a pathogen species. B. Offers immediate cell death to isolated diseased areas. C. Strong but effective against all pathogen races. D. Controlled by a few major resistance genes. Answer: Weak but effective against all races of a pathogen species. (A) Horizontal resistance is controlled by many minor resistance genes and is weaker but effective against all races of a pathogen. 197. Which term best describes the rapid death of cells in response to pathogen attack as proposed by E. Gaümann? A. Hypersensitivity B. Programmed cell death C. Systematic resistance D. Cellular necrosis Answer: Hypersensitivity (A) Hypersensitivity involves the immediate death of both the attacked cells and some adjacent cells to isolate the pathogen. 198. What role did phytoalexins play in plant disease resistance starting in the 1960s? A. They provide structural support to damaged tissues. B. They act as toxic compounds against pathogens. C. They boost the efficiency of major resistance genes. D. They enhance nutrient uptake in resistant varieties. Answer: They act as toxic compounds against pathogens. (B) Phytoalexins are toxic compounds that contribute to disease resistance in certain plants. 199. What was the significance of Mills' 1944 research regarding plant disease epidemiology? A. It established the genetic basis of plant resistance. B. It identified key host-pathogen compatibility factors. C. It correlated rain duration with temperature for infection prediction. D. It introduced the concept of disease resistance mechanisms. Answer: It correlated rain duration with temperature for infection prediction. (C) Mills developed a table that linked the duration of rain needed at specific temperatures for apple trees to become infected. 200. Which of these diseases is linked to the massive eradication of trees in the U.S.? A. Citrus canker B. Fire blight of pome fruits C. Apple scab D. Bacterial wilt Answer: Citrus canker (A) Citrus canker caused the eradication of millions of trees in Florida during significant outbreaks in the 1910s and again in subsequent decades. 201. Which type of resistance is defined by being effective against one or few pathogen races but is considered strong? A. Vertical resistance B. Acquired resistance C. Constitutive resistance D. Horizontal resistance Answer: Vertical resistance (A) Vertical resistance is characterized by strong effects but limited efficacy against numerous pathogen races. 202. What is a key feature of the resistance strategy associated with hypersensitivity in plants? A. Long-term stunted growth of the plant B. Rapid symptom development C. Isolation of the pathogen through cell death D. Delayed cell response Answer: Isolation of the pathogen through cell death (C) Hypersensitivity involves the immediate death of attacked and adjacent cells, isolating the pathogen. 203. In which year did Mills create a predictive table for the infection of apple trees? A. 1946 B. 1965 C. 1963 D. 1944 Answer: 1944 (D) Mills developed the predictive table in 1944 to understand how rain duration affects apple disease infection. 204. What is indicated by the phrase 'caused eradication of millions of trees' in reference to citrus canker? A. It led to economic growth in Florida. B. It resulted in significant agricultural losses. C. It improved soil health in infected areas. D. The disease is easily controlled. Answer: It resulted in significant agricultural losses. (B) Citrus canker caused significant economic and agricultural losses due to the destruction of vast numbers of trees. 205. Which of the following best describes the impact of disease resistance mechanisms on plant health? A. They contribute to plant longevity but not immediate health. B. They only prevent minor pathogens. C. They create a barrier against all infection types. D. They enable plants to survive various pathogen races. Answer: They enable plants to survive various pathogen races. (D) Disease resistance mechanisms help plants withstand attacks from multiple pathogen races, contributing to overall health. 206. What type of symptom is characterized by excessive growth of plant parts or organs? A. Necrotic symptoms B. Hyperplastic symptoms C. Abscission symptoms D. Hypoplastic symptoms Answer: Hyperplastic symptoms (B) Hyperplastic symptoms refer to overdevelopment of plant parts or organs. 207. Which disease is known to have caused significant economic losses in the Philippines due to a viroid? A. Cadang-cadang disease B. Tomato spotted wilt virus C. Tomato yellow leaf curl D. Barley yellow dwarf Answer: Cadang-cadang disease (A) Cadang-cadang disease has caused over $200M in losses in the Philippines. 208. Which symptom involves premature falling of leaves due to plant disease? A. Abscission B. Blast C. Hyperplasia D. Rusetting Answer: Abscission (A) Abscission is the term used for the premature falling of leaves. 209. What are necrotic symptoms primarily associated with in plant diseases? A. Cell or tissue death B. Cell or tissue growth C. Failure to differentiate D. Increased cellular number Answer: Cell or tissue death (A) Necrotic symptoms indicate protoplast, cell, or tissue death. 210. What is the primary cause of hyperplastic symptoms in plants? A. Increase in the number of cells B. Failure of tissue differentiation C. Reduction in cell size D. Cell death from necrosis Answer: Increase in the number of cells (A) Hyperplastic symptoms are a result of an abnormal increase in the number of cells. 211. What type of pathogen causes severe losses on tomatoes and tobacco worldwide? A. Viroid B. Virus C. Bacterium D. Fungus Answer: Virus (B) The tomato spotted wilt virus is a significant pathogen affecting crops like tomatoes and tobacco. 212. Which condition is particularly associated with the excessive swelling of the bark above an injury? A. Chlorosis B. Canker C. Gall formation D. Hyperplasia Answer: Gall formation (C) Gall formation involves abnormal growth due to injury responses. 213. Which disease is notably important for small grains on a global scale? A. Tomato spotted wilt virus B. Tomato yellow leaf curl C. Barley yellow dwarf D. Cadang-cadang disease Answer: Barley yellow dwarf (C) Barley yellow dwarf is particularly significant for small grains worldwide. 214. Which symptom represents an abnormal roughening of fleshy organs? A. Rusetting B. Canker C. Blast D. Chlorosis Answer: Rusetting (A) Rusetting is characterized by a superficial brownish roughening of fleshy organs. 215. What type of symptom is caused by protoplast and tissue damage in plants? A. Hypertrophic symptoms B. Hyperplastic symptoms C. Hypoplastic symptoms D. Necrotic symptoms Answer: Necrotic symptoms (D) Necrotic symptoms are indicative of protoplast, cell, or tissue death. 216. Which of the following statements about the emergence of resistance in pathogens is true? A. Only few strains of fungi were resistant to fungicides to begin with in the 1960s. B. Antibiotic resistance was first observed in plant pathogens during the 1950s. C. Resistance in bacteria became significant with the introduction of tetracycline antibiotics in 1967. D. The widespread use of the first systemic fungicides in the 1970s coincided with the appearance of many resistant fungal strains. Answer: The widespread use of the first systemic fungicides in the 1970s coincided with the appearance of many resistant fungal strains. (D) The introduction of systemic fungicides led to a significant emergence of resistant fungi. 217. Which discovery was pivotal in demonstrating the relationship between microorganisms and plant diseases? A. The dithiocarbamate fungicide invention. B. The publication of 'The Origin of Species' by Charles Darwin. C. The establishment of Koch's postulates. D. The discovery of organic mercury compounds. Answer: The establishment of Koch's postulates. (C) Koch's postulates served as a fundamental framework for linking microorganisms to specific diseases. 218. Which event marked the initial use of antibiotics against bacteria in agriculture? A. The use of streptomycin in the 1950s. B. The widespread use of tetracycline in 1967. C. The first dithiocarbamate fungicide invention in 1934. D. The introduction of penicillin by Alexander Fleming in 1928. Answer: The use of streptomycin in the 1950s. (A) Streptomycin was introduced in the 1950s as the first antibiotic used in agriculture. 219. What significant conclusion did Louis Pasteur reach in his research related to disease causation? A. Antibiotics are ineffective against bacterial infections. B. Microorganisms arise spontaneously from non-living matter. C. Plant diseases are exclusively caused by fungi. D. Most infectious diseases are caused by pre-existing microorganisms. Answer: Most infectious diseases are caused by pre-existing microorganisms. (D) Pasteur established that most infectious diseases are caused by microorganisms that arise from pre-existing ones. 220. What was a significant finding of Pier Antonio Micheli in 1729? A. He was the first to classify systemic fungicides. B. He discovered the process of fermentation in plant diseases. C. He described numerous new fungi and challenged the idea of spontaneous generation. D. He discovered that smut spores seed diseased plants. Answer: He described numerous new fungi and challenged the idea of spontaneous generation. (C) Micheli made significant contributions to mycology and contested the notion of spontaneous generation. 221. Which finding is associated with Anton deBary's research during 1861-1863? A. He described the first systemic fungicide. B. He first observed nematodes in agriculture. C. He was the first to document the resistance of fungi to pesticides. D. He confirmed that potato late blight is caused by a fungus. Answer: He confirmed that potato late blight is caused by a fungus. (D) DeBary's work was significant in elucidating the fungal cause of potato late blight. 222. What aspect did Robert Petri contribute to the field of microbiology? A. He invented artificial nutrient media using Petri dishes. B. He established the first protocols for plant necropsies. C. He developed the first systemic fungicides. D. He discovered the antibiotic properties of certain fungi. Answer: He invented artificial nutrient media using Petri dishes. (A) Petri's invention of artificial nutrient media allowed for the culture of microorganisms. 223. What was the primary focus of Kühn's book published in the 1870s? A. Diseases of cultivated crops, examining their causes and effects. B. The prevention and treatment methods for plant diseases. C. The economic impacts of plant diseases in agriculture. D. The identification of new plant pathogens. Answer: Diseases of cultivated crops, examining their causes and effects. (A) Kühn's work was foundational in plant pathology, examining various plant diseases and their causes. 224. Which symptom is associated with hyperplastic conditions in plants? A. Premature falling of leaves B. Yellowing of leaves C. Excessive swelling of tissue D. Sudden death of buds Answer: Excessive swelling of tissue (C) Hyperplastic symptoms involve the abnormal increase in the number of cells, leading to tissue overgrowth. 225. Which of the following plant diseases is known to cause significant economic losses primarily in the Philippines? A. Barley yellow dwarf B. Cadang-cadang disease C. Tomato spotted wilt virus D. Tomato yellow leaf curl Answer: Cadang-cadang disease (A) Cadang-cadang disease has caused the Philippines to incur over $200 million in losses since its observation. 226. What defines necrotic symptoms in plants? A. Overdevelopment of plant organs B. Premature leaf drop C. Failure to differentiate plant parts D. Death of cells or tissues Answer: Death of cells or tissues (D) Necrotic symptoms indicate cell or tissue death, leading to visible damage in plants. 227. Which type of symptom is characterized by a significant increase in cell size within plant tissues? A. Hypertrophy B. Hypoplasia C. Chlorosis D. Abscission Answer: Hypertrophy (A) Hypertrophy refers to the overdevelopment of plant parts due to an increase in cell size. 228. Which plant disease's impact is primarily associated with the Mediterranean region and has resulted in severe losses? A. Tomato spotted wilt virus B. Barley yellow dwarf C. Tomato yellow leaf curl D. Plum pox Answer: Tomato yellow leaf curl (C) Tomato yellow leaf curl virus significantly affects crops such as tomatoes and beans in Mediterranean countries. 229. What hormone was identified as being produced by the agent of fasciation disease in peas? A. Indoleacetic acid B. Gibberellin C. Cytokinin D. Kinetin Answer: Cytokinin (C) Cytokinin was produced by the agent of fasciation disease, leading to the characteristic symptoms. 230. Which organism was shown to induce crown gall disease by introducing Transforming DNA into plant cells? A. Rhizoctonia solani B. Agrobacterium tumefaciens C. Fusarium oxysporum D. Pseudomonas syringae Answer: Agrobacterium tumefaciens (B) Agrobacterium tumefaciens is known for causing crown gall disease through genetic transformation of plant cells. 231. What is the primary characteristic of pathogenicity in plant pathogens? A. Ability to produce spores B. Ability to photosynthesize C. Ability to cause disease D. Ability to survive in extreme conditions Answer: Ability to cause disease (C) Pathogenicity is defined as the ability of a pathogen to cause disease by interfering with essential plant functions. 232. What disease was discovered to be caused by viroids according to the findings of Diener? A. Tomato blight B. Potato spindle tuber C. Crown gall D. Cereal rust Answer: Potato spindle tuber (B) Diener identified that viroids are responsible for potato spindle tuber disease. 233. In which decade did researchers show that certain microbes produced plant hormones like indoleacetic acid? A. 1950s B. 1930s C. 1940s D. 1960s Answer: 1950s (A) The 1950s saw the demonstration that some microbes produced plant hormones like indoleacetic acid. 234. What significant development in plant pathology did Vanderplank contribute in the mid-1960s? A. Identification of plant hormones B. Discovery of viroids C. Observation of mollicutes D. Foundation of epidemiology Answer: Foundation of epidemiology (D) Vanderplank's work established epidemiology as an important field within plant pathology. 235. Which disease is associated with the cereal rust fungus Puccinia graminis, as discovered by Eriksson in 1894? A. Crown gall disease B. Cereal rust disease C. Leaf spot disease D. Potato blight Answer: Cereal rust disease (B) Eriksson's research revealed the different biological races of Puccinia graminis related to cereal rust disease. 236. What type of parasite develops intimately with a plant and multiplies at its expense? A. Saprophyte B. Plant parasite C. Pathogenic fungus D. Mutualistic symbiont Answer: Plant parasite (B) A plant parasite is characterized by its close relationship with the plant, deriving nourishment from it. 237. By which year had several microbial pathogens been shown to produce gibberellins? A. 1971 B. 1939 C. 1963 D. 1950 Answer: 1950 (D) The discovery in the 1950s highlighted the role of microbes in producing gibberellins, a plant growth regulator. 238. What is the primary function of the hormone gibberellin identified in 1939? A. Inhibition of growth B. Induction of flowering C. Stimulation of root development D. Promotion of stem elongation Answer: Promotion of stem elongation (D) Gibberellin plays a crucial role in promoting stem elongation and growth in plants. 239. What was the cause and impact of the Irish famine in 1845-46? A. Late blight of potato, leading to significant food loss B. Southern corn leaf blight, resulting in crop failure C. Brown spot of rice, leading to mass starvation D. Chestnut blight, causing economic collapse in the UK Answer: Late blight of potato, leading to significant food loss (A) The late blight of potato is associated with annual epidemics and led to the Irish famine. 240. Which disease is associated with the production of aflatoxin and is notably carcinogenic? A. Chestnut blight B. Downy mildew of corn C. Downy mildew of tobacco D. Powdery mildew of grapes Answer: Downy mildew of corn (B) Aflatoxin is produced by A.flavus, which is associated with downy mildew of corn. 241. Which disease led to the destruction of almost all American chestnut trees between 1904 and 1940? A. Brown spot of rice B. Southern corn leaf blight C. Ergot of rye D. Chestnut blight Answer: Chestnut blight (D) Chestnut blight significantly diminished the American chestnut population. 242. What was a significant consequence of the great Bengal famine in 1943? A. Linked to powdery mildew of grapes B. Triggered by brown spot of rice epidemics C. Resulted from chestnut blight D. Caused by late blight of potato Answer: Triggered by brown spot of rice epidemics (B) The great Bengal famine was significantly influenced by epidemics of brown spot of rice. 243. Which of the following pathogens is linked to a significant reduction in corn quality and produces yellow rice toxins? A. A.flavus B. P.philippinensis C. Penicillium spp. D. Fusarium graminearum Answer: P.philippinensis (B) Downy mildew of corn is associated with P.philippinensis and produces harmful yellow rice toxins. 244. Which pathogen is infrequently found but is poisonous to humans and animals? A. C.purpurea B. F.graminearum C. P.infestans D. A.flavus Answer: C.purpurea (A) Ergot of rye and wheat, caused by C.purpurea, is infrequently found and poisonous. 245. What is one of the economic impacts of the Southern corn leaf blight epidemic in the U.S. in 1970? A. Estimated $100 million lost B. Around $500 million lost C. Approximately $1 billion lost D. $2 billion lost Answer: Approximately $1 billion lost (C) The Southern corn leaf blight epidemic in 1970 resulted in an economic loss of about $1 billion. 246. What impact did the epidemics of downy mildew of tobacco have in North America in 1979? A. Catastrophic loss of chestnut trees B. Contamination with high estrogen levels C. Massive decline in tobacco yield D. Introduction of cancer-causing agents Answer: Massive decline in tobacco yield (C) The epidemics of downy mildew of tobacco caused significant declines in tobacco yields. 247. Which toxin is produced by the fungus A.ochraceus and is associated with downy mildew of tobacco? A. Yellow rice toxin B. Estrogenic factor C. Ochratoxin D. Aflatoxin Answer: Ochratoxin (C) Ochratoxin, produced by A.ochraceus, is linked to downy mildew of tobacco and can cause liver cancer. 248. What type of climate is primarily affected by late blight of potato? A. Hot and humid climates B. Dry and arid climates C. Temperate climates D. Cool, humid climates Answer: Cool, humid climates (D) Late blight of potato occurs in cool, humid climates, resulting in annual epidemics. 249. What is the primary characteristic of biotrophs in plant pathology? A. They thrive on dead organic matter. B. They exhibit necrotrophic behavior. C. They can grow in both living and dead hosts. D. They can only reproduce in living hosts. Answer: They can only reproduce in living hosts. (D) Biotrophs or obligate parasites can grow and reproduce only in living hosts. 250. Which classification of parasites are known to grow on both living and dead materials but primarily remain as parasites? A. Necrotrophs B. Facultative saprophytes C. Obligate parasites D. Semi-biotrophs Answer: Semi-biotrophs (D) Semi-biotrophs or facultative saprophytes can live as parasites but can also grow on dead organic matter under certain conditions. 251. What significant relationship was established by H.H. Flor in 1946? A. The impact of soil composition on plant disease susceptibility. B. The correlation between temperature and pathogen virulence. C. The relationship between plant size and disease resistance. D. The gene-for-gene relationship between host and pathogen. Answer: The gene-for-gene relationship between host and pathogen. (D) Flor showed that for each gene of resistance in the host, there was a corresponding gene for avirulence in the pathogen. 252. What concept did Orton distinguish in his 1909 research? A. Variability of soil nutrients affecting plant health. B. Mendelian inheritance of plant traits. C. The differences between disease escape, endurance, and resistance. D. Mechanisms of plant photosynthesis. Answer: The differences between disease escape, endurance, and resistance. (C) Orton distinguished between disease resistance, escape, and endurance in plants. 253. What paves the way for the genetic variability within a pathogen species as identified by Barrus in 1911? A. Environmental changes affecting microbial growth. B. Different pathogen races being restricted to specific host varieties. C. The influence of pesticides on pathogen mutations. D. Genetic imbalance resulting from crossbreeding. Answer: Different pathogen races being restricted to specific host varieties. (B) Barrus showed that different pathogen races are restricted to certain varieties of a host species. 254. Which type of response is characterized by the death of both attacked and adjacent cells in plants? A. Systemic acquired resistance B. Adaptive immune response C. Acclimatization mechanism D. Hypersensitive response Answer: Hypersensitive response (D) The hypersensitive response involves immediate cell death to isolate pathogens. 255. What did Biffen report regarding the inheritance of resistance in wheat varieties in 1905? A. Resistance is influenced by soil conditions. B. Resistance occurs only in hybrid varieties. C. Resistance traits are polygenic. D. Resistance was inherited in a Mendelian fashion. Answer: Resistance was inherited in a Mendelian fashion. (D) Biffen reported that the inherited resistance of two wheat varieties to a rust fungus follows Mendelian inheritance patterns. 256. How do facultative parasites operate in relation to living and dead plant materials? A. They switch between parasitic and saprophytic lifestyles. B. They detach from hosts to grow saprophytically. C. They primarily live saprophytically on dead matter. D. They only affect living tissues. Answer: They switch between parasitic and saprophytic lifestyles. (A) Facultative parasites can behave as necrotrophs by attacking living plants and can also grow saprophytically on dead organic matter. 257. What does the term necrotroph refer to in plant pathology? A. Pathogens that feed on dead organic matter for sustenance. B. Parasites that can only survive on dead organic material. C. Organisms that thrive only on living plants. D. Species that have no preference for living or dead plant material. Answer: Pathogens that feed on dead organic matter for sustenance. (A) Necrotrophs are organisms that predominantly thrive on dead organic matter. 258. What significant observation did Z. Klement and colleagues make in 1964? A. The relation of photosynthesis to plant disease. B. Environmental stressors as triggers for fungal infections. C. The hypersensitive response operates against bacterial plant pathogens. D. The role of nutrition in microbial virulence. Answer: The hypersensitive response operates against bacterial plant pathogens. (C) Klement and colleagues recognized the hypersensitive response which operates against bacterial plant pathogens. 259. Which of the following describes chlorosis in plants? A. A condition of leaf curling due to water stress. B. Yellowing of leaves not due to light deficiency. C. A symptom of wilting due to root damage. D. Yellowing of leaves caused by a pathogen. Answer: Yellowing of leaves not due to light deficiency. (B) Chlorosis refers specifically to yellowing of leaves that occurs without light deficiency. 260. What is the defining characteristic of die-back in plants? A. Unusual swelling in bark tissues. B. Rapid decay in root systems. C. Total leaf loss in a tree. D. Drying backward from the tip of the plant. Answer: Drying backward from the tip of the plant. (D) Die-back is a specific condition where the plant exhibits drying starting from the tips. 261. Which term refers to the large, irregular spots on leaves or fruits due to necrotic injury? A. Blotching B. Scab C. Savoying D. Canker Answer: Blotching (A) Blotching is characterized by large, irregular spots caused by necrotic damage to the plant. 262. What does the term 'shot-hole' refer to in plant pathology? A. Perforated appearance of leaves with dead areas dropping out. B. A form of necrosis leading to leaf drop. C. Localized swelling on branches. D. Irregular patterns caused by insect damage. Answer: Perforated appearance of leaves with dead areas dropping out. (A) Shot-hole appearance occurs when dead areas of leaves drop out, creating a perforated look. 263. Which plant condition is identified as canker? A. A sunken necrotic area with a cracked border. B. A drying backward indicative of root damage. C. An overgrowth of tissues around wounds. D. Yellowing leaves caused by poor light exposure. Answer: A sunken necrotic area with a cracked border. (A) Canker is characterized by a distinct sunken area surrounded by cracked borders, indicating tissue death. 264. What significant role did Rachel Carson's 'Silent Spring' play in the 1960s? A. It offered new methods for indoor pest control. B. It provided insights into plant breeding techniques. C. It raised awareness about environmental pollution from pesticides. D. It introduced biological pest control using nematodes. Answer: It raised awareness about environmental pollution from pesticides. (C) Rachel Carson's work highlighted the dangers associated with the use of chemical pesticides in agriculture. 265. Which of the following describes antagonistic microbes used in plant disease control? A. They are exclusively plant-derived fungi. B. They require high temperatures to be effective. C. They compete with pathogens and inhibit their effects. D. They promote the growth of harmful pathogens. Answer: They compete with pathogens and inhibit their effects. (C) Antagonistic microbes are beneficial as they help suppress disease-causing pathogens. 266. The discovery of suppressive soils in the early 20th century is significant because they: A. Contain high levels of pesticide residues. B. Are only effective in certain climatic conditions. C. Naturally protect against certain plant diseases. D. Require chemical interventions for efficiency. Answer: Naturally protect against certain plant diseases. (C) Suppressive soils increase resilience in plants against diseases through their unique microbial communities. 267. What was the first pathogen identified to cause diseases in plants? A. Fusarium oxysporum B. Smut spores C. Phytophthora infestans D. Hyaloperonospora parasitica Answer: Smut spores (B) The smut spores identified by Prevost in 1807 were the first known plant pathogens linked to disease. 268. What is cross protection as discovered in the early 1930s? A. Antagonism between different strains of the same virus to provide immunity. B. Application of multiple chemical pesticides at once. C. The introduction of genetically modified organisms for pest resistance. D. The use of antibiotics to treat all types of plant diseases. Answer: Antagonism between different strains of the same virus to provide immunity. (A) Cross protection refers to the ability of one viral strain to provide resistance against another strain in plants. 269. As of 1963, which significant approach was first controlled in plant disease management? A. Use of antagonists like Pseudomonas gigantea. B. Use of transgenic plants. C. Cultivation of hybrid crops. D. Application of mercury-based pesticides. Answer: Use of antagonists like Pseudomonas gigantea. (A) The controlled use of antagonists to target specific plant diseases marked a major advancement in biological control methods. 270. Which of the following pathogens is associated with the early identification of nematodes? A. Root-knot nematode observed by Needham. B. Phytophthora infestans characterized by Prevost. C. Cyst nematode first seen by Fleming. D. Meloidogyne hapla discovered by Anton deBary. Answer: Root-knot nematode observed by Needham. (A) Needham was the first to observe nematodes, specifically the root-knot nematode in cucumber galls. 271. The banning of certain chemical pesticides in the 1960s coincided with what discovery about their dangers? A. They are effective in controlling all types of pests. B. They contribute to genetic resistance in plants. C. They pose a risk to human health and the environment. D. They enhance soil fertility. Answer: They pose a risk to human health and the environment. (C) The recognition of the health and environmental risks posed by chemical pesticides led to their regulation and banning. 272. Which disease is responsible for the historical epidemic that contributed to the Irish famine between 1845 and 1846? A. Late blight of potato B. Brown spot of rice C. Downy mildew of tobacco D. Southern corn leaf blight Answer: Late blight of potato (A) Late blight of potato, caused by *P. infestans*, was a critical factor in the Irish famine. 273. What was the primary impact of the brown spot of rice epidemic during the great Bengal famine of 1943? A. Complete destruction of crops B. Transmission of toxins to consumers C. Increased food prices D. Reduction in quality of produce Answer: Reduction in quality of produce (D) The brown spot of rice caused a significant reduction in the quality of rice during the Bengal famine. 274. Which toxin produced by *A. flavus* is known to be carcinogenic? A. Yellow rice toxin B. Ochratoxin C. Estrogenic factors D. Aflatoxin Answer: Aflatoxin (D) Aflatoxin, produced by the fungus *A. flavus*, is a known carcinogen and is found in crops such as corn. 275. What was the economic consequence of the southern corn leaf blight epidemic in 1970? A. $200 million lost B. $1 billion lost C. $2 billion gained D. $500 million saved Answer: $1 billion lost (B) The southern corn leaf blight epidemic caused significant economic losses, estimated at $1 billion. 276. Which disease led to the near extinction of American chestnut trees between 1904 and 1940? A. Southern corn leaf blight B. Downy mildew of tobacco C. Chestnut blight D. Late blight of potato Answer: Chestnut blight (C) Chestnut blight decimated nearly all American chestnut trees, showcasing the devastating impact of a single pathogen. 277. Which disease is known to cause losses in corn amounting to over P170M annually due to its high impact? A. Downy mildew of corn B. Chestnut blight C. Brown spot of rice D. Ergot of rye Answer: Downy mildew of corn (A) Downy mildew of corn significantly affects the yield, leading to substantial economic losses annually. 278. Which disease is responsible for serious losses in rubber tree plantations? A. Citrus tristeza B. Sugar beet yellows C. Rubber leaf blight D. Fusarium scab of wheat Answer: Rubber leaf blight (C) Rubber leaf blight specifically targets rubber trees, causing significant damage to plantations. 279. What catastrop