Plant Pathology Lecture Notes PDF

PLANT PATHOLOGY Unit 3 PREPARED BY: MS. MEDEL L. CEKO  Page i ᴥ Plant Pathology ᴥ Economic Importance Of Plant TOPICS Diseases ᴥ History of Plant Pathology ᴥ Concept Of Plant Diseases (LECTURE): :...

PLANT PATHOLOGY Unit 3 PREPARED BY: MS. MEDEL L. CEKO  Page i ᴥ Plant Pathology ᴥ Economic Importance Of Plant TOPICS Diseases ᴥ History of Plant Pathology ᴥ Concept Of Plant Diseases (LECTURE): : ᴥ Causes Of Plant Diseases ᴥ Disease Cycle ᴥ Plant Disease Epidemiology ᴥ Variability In Plant Pathogens  Page i ᴥ Familiarize the part of the TOPICS Microscope ᴥ Disease symptoms Identification (Collection) (LABORATORY): : ᴥ Plant Disease Development (Group Project: Penetration, Dissemination, Survival)  Page 01 PLANT PATHOLOGY ❑Pathos- suffering ❑Logos- to study “ the study of the suffering plant” Ultimate Goal: Manage plant disease so that losses will be brought at minimum.  Page 01 PLANT PATHOLOGY Studies the living entities and the environmental conditions that cause disease in plants Studies the interactions between the disease-causing agents and the diseased plant Studies the methods of preventing or controlling disease and alleviating the damage it causes  Page 02 AGRICULTURE IS THE STUDY OF ART AND SCIENCE… THEREFORE, Crop Protection specifically Plant Pathology… Defined as a SCIENCE because it seeks to understand the NATURE of plant diseases. a. Disease Characteristics b. Agents, Host pathogen interaction c. Disease development, and its control measure  Page 02 AGRICULTURE IS THE STUDY OF ART AND SCIENCE… THEREFORE, Crop Protection specifically Plant Pathology… Defined as a ART because it is the application of knowledge gained from studying the nature of plant diseases. a. Diagnoses and assessment b. Forecasting and prevention c. Pesticide application and pest management  Page 03 CONCEPT OF DISEASE WHAT IS DISEASE? ᴥ Series of invisible and visible responses of plant cells and tissues to a pathogenic microorganism or to an unfavorable environmental factor that result in adverse changes in the form, function or integrity of the plant and may lead to partial impairment or death of the plant or its parts  Page 03 CONCEPT OF DISEASE According to Agrios, disease is defined as… -Any malfunctioning of host cells and tissues that results from continuous irritation by a pathogen or environmental factor and leads to a development of symptoms  Page 03 CONCEPT OF DISEASE Stackman and Harrar (1957) – any deviation from normal growth or structure of plants that is sufficiently pronounced and permanent to produce visible symptoms or to impair quality or economic value.  Page 03 CONCEPT OF DISEASE Merill (1980) - a dynamic interaction between an organism and its environment which result in abnormal physiological and often morphological or neurological changes in the organism.  Page 04 Schematic representation of the basic functions in a plant (left) and the interference with these functions (right) caused by some common types of plant diseases (Agrios, 2005)  Page 05 1. Plant diseases endanger food Importance of Plant Disease supply 2. Reduce the quantity and quality of plant produce. 3. Cause financial losses 4. Limit the kinds of plants and : industries in an area. 5. Make plants poisonous to humans 6. Increase cost of production due to control measures  Page 05 Directly related to importance of Importance of Plant Disease plants as: 1. Food 2. Shelter Plant diseases damage plants 3. Clothing and plant 4. Medicine products 5. Aesthetics 6. Improving environment 7. Luxuries  Page 07 SHORT HISTORY AND IMPORTANCE (Prominent Plant Diseases in World History) Late Blight Disease of Potato ( Phytophthora infestans) - 15 % worldwide, 2.75 Billion US$ losses in Dev. Countries, with fungicide costs ~3 Billion US$ ❑ Devastated Northeastern Europe as potato is its staple crop ❑ 1845 - observed in Belgium, Holland, England, and Ireland (25% losses incurred) ❑ 1846 - total crop failure in Ireland caused the Irish Famine  Page 07 SHORT HISTORY AND IMPORTANCE  Page 07 SHORT HISTORY AND IMPORTANCE Coffee Rust in Ceylon (now Sri Lanka)(Hemilea vastatrix). ❑ 1835 British people planted 200 hectares ❑ 1875 booming economy (200,000 hectares;50M kg/ year) ❑ Destroyed coffee plantations; tea was planted insteads  Page 07 SHORT HISTORY AND IMPORTANCE  Page 07 SHORT HISTORY AND IMPORTANCE Ergot of Rye (Claviceps purpurea). ❑ From the french word "argot" meaning"spur". ❑ Produces alkaloids including lsd (LysergicAcid DiethylamideL,a well- known hallucinogenic drug. ❑ Caused abortion, tingling sensation, fever, gangrene, convulsions, hallucinations. ❑ 1722 - influenced the outcome of a war in Astrakhan, the army of Peter the Great of Russia (20,000 soldiers) died from consuming bread made from severely infected wheat  Page 07 SHORT HISTORY AND IMPORTANCE  Page 07 SHORT HISTORY AND IMPORTANCE Bengal Famine (before: Helminthosporium oryzae)(Now: Cochliobolus miyabeanus, Bipolaris oryzae) ❑ Brown Spot of Rice. ❑ Bangladesh; 50% yield loss for early maturing varieties; 75-90% yield loss for late maturing varieties  Page 07 SHORT HISTORY AND IMPORTANCE (Prominent Plant Diseases in Philippine History) Cadang-Cadang Disease of Coconut ❑ Caused by viroid ❑ First observed in 1918; loss amounted to >$2oo million; killed 15M tress Downey Mildew of Corn ❑ Caused by Peronoscleorpora philippinensis ❑ Annual yield loss reached 95% amounting to 170 M ❑ Controlled by the seed treantment using Metalaxyl  Page 07 SHORT HISTORY AND IMPORTANCE (Prominent Plant Diseases in Philippine History)  Page 07 SHORT HISTORY AND IMPORTANCE (Prominent Plant Diseases in Philippine History)  Page 07 Rice Tungro ❑ Caused by a Rice Tungro Bacilliform Virus (RTBV) and Rice Tungro Spherical Virus (RTSV)· ❑ Affected 70,000 hectares in 1971. ❑ Losses of 1.22M canvas of rice valued at more than P30M Coffee Rust ❑ Caused by a Hemileaia vastatrix ❑ Destroyed Coffee Industry in Batangas Citrus Decline ❑ Caused by a Tylenchulus semipenetrans. ❑ Wiped out Citrus plantations in Batangas Page 07  Page 07 Disease Causal Agent Host Impact Ergotism Claviceps purpurea Triticum aetivum Sickness and Disease in humans Late Blight Phythopthora infestans Potato Irish Famine Coffee Rust Hemeleia vastatrix Coffee Switch to Tea Cadang-cadang Cadang cadang viroid Coconut 200 M USD in losses Rice Tungro Rice Tungro Bacilliform Rice 1.22 M cavans lost, Virus, Rice Tungro 30M php in losses Spherical Virus Downy Mildew Peronosclerospora Corn 170 M Php losses philippinensis anually  Page 08 HISTORICAL DEVELOPMENT Pre- Scientific Period Fossil Records (Ancient Writings) HOMER- 1000 BC; mentioned therapeutic properties of Sulfur in plant diseases. BIBLE (stated)- 750 BC; time of Joseph the dreamer- Wheat Rust;. - Egypt- warm and windy Mildews. Blasts and Blights of Cereals  Page 08 HISTORICAL DEVELOPMENT Pre- Scientific Period Fossil Records (Great Philosophers) DEMOCRITUS- 470 bc, noted Plant Blights and described ways to control it. PLINY THE ELDER- wrote about blights and rusts in Historia naturalis. THEOPHRASTUS - 370-286 bc, Father of Botany ❑ First to make plants and plant diseases as subjects of systematic study. ❑ Wrote The Nature of Plants (morphology and anatomy of plants, descriptions of wild and cultivated plants, and Reasons of Vegetable Growth  Page 08 HISTORICAL DEVELOPMENT Pre- Scientific Period Fossil Records (Great Philosophers) GREEKS AND HEBREWS – 500-280 BC - diseases are punishment to sins due to bad weather and unfavorable conditions. ROMANS- 320 BC- 475 AD - held an annual festival called Robigalia in attempt to please and pacify the Rust God, Robigus and Robigo so that they would not send the rusts to destroy their crops.  Page 08 HISTORICAL DEVELOPMENT Pre- Scientific Period Fossil Records (Great Philosophers) Ergot of Rye and Wheat Epidemic in Europe- also known as the Holy Fire or St. Anthony's Fire due to the initial burning sensation felt by the persons afflicted with Ergotism; believed as punishment of man’s sins.  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Theories of Spontaneous Generation (Autogenic Theory of Disease) FRANZ UNGER. - When plants are in the declining phase, the cellular constituents CALL FORTH NEW FORMS OF LIFE by vital force. The pathogen is a result and not the cause of the disease. Some beliefs in the origin of life: Frogs are from mud in the ponds Maggots are from decaying meat Yeasts are from fermented grape juice. Rats are from piles of old clothing  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Experiments that disprove the Theories of Spontaneous Generation REDI (1688)- covered mouth of vessel containing meat with a screen; maggots develop only from eggs of flies and never in meat when flies where kept away. SPALLANZANI (1777)- bacteria did not develop in food materials that have been boiled for sometime and sealed away from air; air is essential for spontaneous generation  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Experiments that disprove the Theories of Spontaneous Generation SCHULZE (1836)- passed air through Sulfuric Acid; introduction of air did not induce development of bacteria. SCHWANN (1837)- passed air through hot tubes. SCHRODER and DUSCH (1854)- filtered air through sterile cotton  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Germ Theory of Disease Louis Pasteur "All living things must come from pre-existing parents“ "Micro-organisms cause the disease and not the effect of the disease“ PIER ANTONIO MICHELLI (1729) - Father of Mycology described many genera of fungi; believed that fungi arose from their own spores; used bunt infected wheat seeds  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Germ Theory of Disease ROBERT HOOKE (1660)- invented early(double-lensed);examined thin slices of cork and called it "cell"; findings published in Micrographia THOULLIER (1670)- observed that Ergotism did not spread from one person to another but seemed to be associated with the consumption of contaminated grains. ANTOINE van LEEWUENHOEK (1683)- first to describe bacteria from teeth scrapings and protozoans from pond water compound microscope  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies Germ Theory of Disease TILLET (1755)- noted that dust from smutted wheat mixed with healthy seeds resulted in smutted wheat plants; noted that he could reduce the number of smutted wheat plants produced by treating the smut- treated kernels with Copper Sulfate PREVOST(1807)- repeated Tillet’s experiment and had the same results; observed and treated smut spores under the microscope·  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD “ Microorganism were discussed to be associated with plant diseases” NEEDHAM (1743)- observed nematodes(Anguina tritici) in Wheat Kernels. TARGIONI-TOZZET (1766) and FONTANA(1767)- studied cereal rust and concluded that rust fungi is associated with the disease  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD “ Microorganism were discussed to be associated with plant diseases” HEINRICH ANTON de BARY (1853)- Father of Plant Pathology; studied Phytophtora infestans, causal organism of Potato Late Blight; proved that stem rust of wheat (Puccinia graminis f.sp. tritici) needs an alternate host (Barberry; where fruiting bodies are formed) to complete its lifecycle  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD THOMAS JONATHAN BURILL (1978-1883)- studied Apple and Pear Blight(Erwinia amylovora). MAYER (1886)- found out that Tobacco Mosaic (Tobacco Mosaic Virus) can be reproduced by inoculating sap of diseased plant to a healthy plant. IVANOWSKI (1892)- demonstrated the filterable nature of TMV BEIJERINCK (1898)- Father of Virology, coined the name "Tobacco Mosaic Virus". BAWDEN (1935)- crystallized TMV  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD DOI, TERENAKA, YORA, and ASUYAMA(1967)- discovered the association of mycoplasma-like organisms (MLOs)/Phytoplasmas in mulberry dwarf, potato witches' broom and aster yellows. DAVIS, WHOELEY, WHITCOMB , ISHIYAMA, STEERE (1972)- observed spiroplasmas associated with Corn Stunt Disease,  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD DOI et al – first reported the mycoplasma- like organism as plant pathogens. Ishiie and co workers- observed that treating infected plans with tetracycline caused a temporary disappearance of the symptoms and the mycoplasma-like bodies. “ Diseases and which mycoplasmas have implicated are lethal yellowing of coconut palms, potato withes, broom. Bunchy top of papaya, rice tallow dwarf, mungbean witches; broom and aster yellows”.  Page 08 HISTORICAL DEVELOPMENT Beginnings of Scientific Studies ETIOLOGICAL PERIOD Davis and co-workers – observed what they called a spiroplasma in 1972. A motile, helical’ microorganism that caused the stunt disease of corn. T.O Diener in 1971- observed viroids as plant pathogens of potato causing the spindle tuber disease. Windor and Black in 1972- discovered that rickettsia-like microorganisms to caused the club leaf of clover.  Page 08 HISTORICAL DEVELOPMENT Plant Pathology in the Philippines 1910 - first course in Plant Pathology was taught as Botany 4 under the Agronomy Department. 1914- Baker- published The Lower Fungi of the Philippines, a review of Philippine Plant Diseases 1917- Department of Plant Pathology was born and the course offered was Plant Pathology. 1917- Otto Reinking- first department head. 1933- Gerardo Ocfemia- Dean of Filipino Plant Pathologists; First Filipino Department Head  Page 08 HISTORICAL DEVELOPMENT Plant Pathology in the Philippines 1885-1890- Batangas Coffee Rust (Hemileia vastatrix). 1908- E.B. Copeland- Coconut Bud Rot (Phytophtora palmivora). 1911- Robinson- Corn Leaf Blight (Helminthosporium maydis). 1912- Baker; 1920-1923-Weston- Downy Mildew of Corn (Peronosclerospora philippinensis). 1920-1940-G.Q. Ocfemia- Abaca Bunchy Top. 1950-1960- studies on the etiology and control of leaf and seedling diseases; development program in upgrading staff and physical facilities  Page 08 HISTORICAL DEVELOPMENT Plant Pathology in the Philippines 1978- Exconde et al- controlled the Corn Downey Mildew by seed treatment using Metalaxyl. 1983- Romulo Davide- developed Biocon Paecilomyces lilacinus against nematodes  Page 08 Quiz no 2 1. Plant pathology comes from the Greek word pathos and logos that means? 2. Discuss the difference between germ theory and autogenic theory of disease? 3. Father of Botany? 4. They first reported the mycoplasma- like organism as plant pathogens.? 5. He developed Biocon Paecilomyces lilacinus against nematodes?  Page 08 Quiz no 2 6. He believed that fungi arose from their own spores? 7. Also known as the Holy Fire or St. Anthony's Fire? 8.Causal agent of Potato Late Blight? 9. Father of Virology? 10. Causal Agent of Bengal Famine or Brown Spot? Parasitism and Disease Development Unit 3.1 PREPARED BY: MS. MEDEL L. CEKO  Page 09 Disease Triangle Concept 1. Central Concept of Plant Pathology 2. Disease is the result of Virulent interaction between a host, a potential pathogen, and the Susceptible Favorable environment.  Page 11 Terms and Terminologies  Page 10 Host- a plant being attacked by parasite. A food relationship with a parasite (pathogen) is implied. Suscept – a plant that is susceptible to a disease whether or not the pathogen is parasitic Pathogen- any agents (biotic and abiotic) that causes a disease. The term is generally used to refers to a living organisms Bacteria: Penicililium notatum Virus Nematodes Fungi Causal agents- the biotic or abiotic factors which, through prolonged irritation, causes the disease  Page 10 Inoculum- any parts of a parasite that can cause infection Hyphae and Conidia Hyphae and Conidia Ascus Zygosporangium Signs- the physical manifestation of the causal agents (structure of the pathogent or the pathogen itself) Example: Conidia, hyphae, bacterial ooze, nematodes larvae or eggs Page 10  Page 10 Symptoms- the physical manifestation of the host’s response (expressions) - evidence of the disease in the plant: visible reaction of the plant due to irritation by the pathogen. Example: Leaf spots, wilting, soft rot, mosaic Click for larger image. Bacterial wilt of cucurbits Tomato Mosaic Virus Alternaria leaf spot  Page 10 Lesion- a well defined localized diseases area Virulence- refers to the quantitative amount of disease that an isolate (pathogen) can cause in a group of plants Disease Resistance - inherent ability of an organism to overcome, in any degree, the effects of a pathogen. Tolerance- exhibited by a plant which is severely affected by a pathogen without experiencing a severe reduction in yield  Page 12 1. Localized vs. Systematic Classification of Symptoms 2. Primary Symptoms vs. Secondary Symptoms 3. Microscopic vs. Macroscopic 4. Histological vs. Morphological  Page 12 Localized vs. Systematic (Mode of Action) 1. Localized Symptoms- - expressed as physiological and structural changes in a limited part of a plant (canker, leaf spots, and gall) - Symptoms occur on specific plant parts  Page 12 Localized vs. Systematic 2. Systemic Symptoms – expressed as the greater reaction of infection to the different parts of the plants (mottle, mosaic and wilting) - All over the plant  Page 12 Primary Symptoms vs. Secondary Symptoms (point of origin) 1. Primary Symptoms - the direct result of pathogen activity on the invaded tissues - At the point of pathogen entry  Page 12 Primary Symptoms vs. Secondary Symptoms (point of origin) 1. Secondary Symptoms - the physiological effects on distant and uninvaded organs - Distant to the point of entry  Page 12 Microscopic vs. Macroscopic Microscopic – expressions of Macroscopic – expressions of the disease in cell structure that the disease in the plants or its can be studied only under a parts that can be studied by the microscope naked eye  Page 12 1. Chlorotic 2. Necrotic 3. Hypoplastic/hypotrophy Macroscopic Symptoms 4. Hyperplastic/hypertrophic Hypertrophy hyperplasia  Page 12 Macroscopic Symptoms 1. Chlorotic- yellower than normal 2. Necrotic – death of tissues; cell degeneration Plesionecrotic- pre-necrotic; near dead  Page 12 Macroscopic Symptoms Chlorosis Necrotic Hypoplastic/ Hypotrophy  Page 12 Macroscopic Symptoms 3. Hypoplastic/hypotrophy- developmental failure ; Stunting due to retarded growth; may involve increased cell division but without corresponding increase in cell volume Example: stunting, chlorosis, mosaic, curling and rosetting.  Page 12 Macroscopic Symptoms Tobacco Mosaic Chlorosis Rosetting Hypoplastic/ Hypotrophy  Page 12 Macroscopic Symptoms 4. Hyperplastic/hypertrophic- overdevelopment or enlargement Example: Crown Gall, scabs, knot Hypertrophy- increase in cell size; no new cell just larger cell Cause: this can be due to various factors such as increased nutrient availability, hormonal changes. Or environmental stress.  Page 12 Macroscopic Symptoms 4. Hyperplastic/hypertrophic- overdevelopment or enlargement Example: Crown Gall, scabs, knot Hyperplasia- increase in cell number; excessive cell division Cause: this often occurs in response to hormonal signals or injury, prompting cells to divide and proliferate  Page 12 Macroscopic Symptoms Hypertrophy: Root Knot Hyperplasia Nematodes in Tomato  Page 12 Histological vs. Morphological Histological – essentially Morphological – those internal and seen only upon the malformations and other dissection of the diseased plant changes on the different parts portion and examination under of the plants that are visible to the microscope (cell the naked eye (e.g. blight, leaf enlargement and vascular spot) discoloration).  Page 11 Terms and Terminologies Parasitism and Pathogenicity  Page 10 Parasitism- Removal of food by a parasite from its host Pathogenicity- Ability of the parasite to interfere with one or more of the essential functions of the plant and thereby to cause disease Parthenogenesis- disease development in the plant Obligate Parasite- Can grow and reproduce in nature only on living host Non-Obligate Parasite- Can live on either living or dead host and on various nutrient media  Page 10 Facultative Parasite- Thrive mostly on dead organic matter, but may attack living plants and become parasitic Saprophyte- Grow and reproduce on dead organic and inorganic matter Facultative Saprophyte- Live most of the time or most of their life cycle as parasites but may grow saprophytically on dead organic matter Masked Symptoms- symptoms not expressed due to unfavorable condition Symptomless carrier- host that does not show symptoms irrespective of environment  Page 11 SYMPTOMS TERMINOLOGIES  Page 10 Abscission - Early laying down of the abscission layer causing premature falling of leaves, fruits or flowers.  Page 10 Blast - Sudden death of young buds, inflorescence or young fruits (Ex: Pyricularia oryzae- Rice Blast).  Page 10 Blight - Sudden and extensive death of tissue(Ex: Fire Blight of Apple). Sheath Blight of Rice Rhizoctonia solani  Page 10 Blotch - Necrotic injury of epidermal cells seen as irregular, large spots in leaves or fruits.  Page 10 Canker - a sunken necrotic area with cracked border Citrus canker Xanthomonas citri  Page 10 Chlorosis - yellowing caused by infection of abiotic factor such as a virus or mycoplasma  Page 10 Curling - abnormal bending of leaves caused by overgrowth on one side or localized growth in certain portions (Ex: Tomato Yellow Leaf Curl).  Page 10 Damping off - rotting of seedlings prior to emergence or rotting of seedling stems at an area just above the soil line (Ex: Pythium sp.-Damping Off of Seedlings).  Page 10 Dieback - A drying of the leaves that happens from the tip of twigs (Papaya Dieback).  Page 10 Etiolation - Yellowing of normally green tissues caused by inadequate light.  Page 10 Fasciation/Fasciculation - clustering of roots, flowers, fruits, or twigs around a common focus.  Page 10 Gumming/Gummosis - Oozing out of viscid gum from wounds in bark.  Page 10 Leak - Host juices exude or leak out from soft-rotted portions.  Page 10 Mosaic - the presence of variegated patterns of green and yellow shades with sharply defined borders (usually in leaves) (Ex:Tobacco Mosaic)  Page 10 Mottling - The variegation is less defined than mosaic and the boundaries of light and dark areas are more defused.  Page 10 Mummification - The infected fruit is converted to a hard, dry, shriveled mummy. Due to the rapid loss of moisture.  Page 10 Phyllody - Metamorphosis of sepals, petals, stamens, or carpels into leaf-like structures. Caused by phytoplasma or virus infections, though it may also be because of environmental factors that result in imbalance in plant hormones  Page 10 Pitting - defined depressions or pits found in surfaces of fleshy organs that appear like pokes and holes.  Page 10 Rosetting - Shortening of shoot internodes and stems forming a foliage crowd in the shape of a rose/rosette.  Page 10 Rotting - Disintegration and decomposition of host tissue  Page 10 Rusetting - Suberization of epidermal tissues due to injury causing rough, brownish appearance of the skin.  Page 10 Sarcody - Abnormal swelling of the bark above wounds due to accumulation of food materials.  Page 10 Savoying - Cupping or pocketing of leaf parts due to underdevelopment of leaf veins or leaf margins.  Page 10 Scab - Overgrowth of epidermal and cortical tissue accompanied with rupture and suberization of cell walls causing slightly raised, rough, ulcer-like lesions..  Page 10 Shothole - perforated appearance of a leaf as the dead areas of local lesions drop out (Ex:Colletotrichum gleoisporiodes; Mango Anthracnose)  Page 10 Spot- localized necrotic area that may be circular, angular, or irregularly shaped (Ex:Gray Leaf Spot of Tomato).  Page 10 Streak/Stripe- long, narrow, necrotic lesions on the leaves or stems (Ex:Helminthosporiun Stripe of Barley)  Page 10 Vein clearing - Leaf veins are translucent or pale yet the rest of the leaf is normal in color  Page 10 Virescence/Greening – development of chlorophyll in tissues or organs where it is normally absent.  Page 11 CATEGORIZATION OF SIGN TERMINOLOGIES  Page 10 1. Vegetative Structures- absorption and nutrients storage; produces for feeding or storage purpose. Example: ooze. Thallus, mycelia, hypha. Sclerotia, rhizomorphs, plasmodium.  Page 10 2. Reproductive Structures- Reproduction, multiplication and transfer of genetic material Fruiting Bodies- Where the spores are formed Example: sporanguim, molds, conks, pycnidia, perithecia, apothecia, mushroom, conidiophore  Page 10 ❖Germs – serve to reproduce the pathogen Examples: spores Sexual Spores - oospore, ascospore basidiospore, Asexual spores - conidia, sporangiospores Motile spores - zoospores  Page 10 3. Disease Products- gases and exudation products resulting from the disease  Page 11 SIGNS TERMINOLOGIES  Page 10 Felt - Densely woven mat of mycelium. Haustorium - Absorbing organ of fungus that penetrates a host cell without penetrating the plasma membrane. Mycelium - Mass of fungal threads or hyphae. Pathogen cells - masses of bacterial cells. Plasmodium - Naked mass of protoplasm. Rhizomorph - cord-like strand of fungal hyphae  Page 10 MYCELIA  Page 10 PLASMODIUM  Page 10 Sclerotium - A hard, compact, resting body composed of fungal hyphae. Acervulus - mat of hyphae, forming lesions with short, densely packed conidiophores Apothecium- Open, cuplike, containing fruiting body. Ascus - sac-like structure containing ascospores formed as a result or karyogamy and meiosis. Basidium - club-shaped structure on which basidiospores are produced as a result of karyogamy and meiosis. Page 10  Page 10 Cleistothecium - closed ascus-containing fruiting body. Conidiophore - specialized hyphal branch on which conidia are produced. Conk- woody shell-like structure characteristics of many woody-rotting fungi. Mildew - cobwebby or powdery growth usually on leaves. Mold - Woolly of furry surface growth of mycelium. Mushroom (toadstool) - Umbrella-shaped fruiting structure of many Basidiomycetes. Perithecium - Fruiting body bearing asci in locules within a stroma.  Page 10 CONK  Page 10 Pseudothecium - Fruiting body bearing asci in locules within a stroma. Pycnidium - Asexual, hollow fruiting body containing conidia. Seed bearing plants - higher plants that parasitize trees. Sorus - mass or cluster of spores borne on short stalks. Sporangium - enlarged tip of specialized hyphal branch in which sporangiospores are borne. Spore - General name for a single to several-celled propagative unit in fungi and other lower plants. Page 10 Page 10  Page 10 Sporodochium- Cushion-shaped stroma covered with conidiosphores. Stroma - Compact mass of fungal hyphae on or within which fruiting structures are formed. Worms - Generally nematodes which are microscopic, wormlike animals that can cause disease. Odor - Characteristic smell associated with some host- pathogen interactions. Ooze - Viscid mass made up of plant juices and often pathogen cells Page 10 Page 10  Page 10 1. Association- Pathogen or its signs must be found associated with the diseases in all the diseases plants examined 2. Isolation- Pathogen must be isolated and grown in pure culture on nutrient media and its characteristics described - Obligate parasites must be isolated and grown on a healthy but susceptible host plant, and its characteristics described  Page 10 3. Inoculation- Pathogen from the pure culture must be inoculated on healthy plants of the same species or variety on which the disease appears, and it must produce the same disease on the inoculated plants 4. Re-isolation- Pathogen must be re-isolated from the inoculated plants and grown once more in pure- culture. - Its characteristics must be exactly like those observed in Step 1 and 2