Questions and Answers
What are the different types of fungal pathogens?
3 - biotrophic, necrotrophic, hemibiotrophic; 6 - monomertrophs; 11 - phylogenetics.
Which methods are used to combat fungal pathogens at a global level?
How are plant diseases classified by phenotype?
By symptom, by host, and by color.
Obligate pathogens can be cultured outside of their host plants.
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What are the classifications of saprotroph, biotroph, and necrotroph?
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Define hemibiotrophy.
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Do biotrophic pathogens feed on dead cells?
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What are some factors of biotrophs?
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What are some factors of hemibiotrophs?
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What are some factors of necrotrophs?
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What are effectors?
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What did scientists start to do when the three classes of pathogens became unclear?
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Study Notes
Classification of Plant Pathogens
- Fungal pathogens are categorized into three main types: biotrophs, necrotrophs, and hemibiotrophs, with additional distinctions of 6 monocotrophs and 11 phylogenetic classifications.
- Global strategies to combat plant pathogens include biosecurity, agronomy, genetic methods, and chemical treatments, with optimization in genetic and chemical approaches emphasized.
Phenotypic Classification of Plant Diseases
- Symptoms can classify plant diseases:
- Pathogen-related symptoms (rust, mildew, smut)
- Host symptoms (blotch, spot, dieback)
- Host-specific classifications include wheat and barley rust.
- Color-based classification includes yellow rust and brown rust.
Classification by Culturability
- Pathogens can be categorized based on culturing:
- Obligate pathogens require living plants to grow, while facultative pathogens can grow on dead organic matter.
- Culturability may not reflect feeding methods in the plant host.
Trophic Classifications
- Saprotrophs feed on dead organic matter; biotrophs consume living plant cells, while necrotrophs feed on dying or dead cells.
- Biotrophs cause symptoms reflective of the pathogen, whereas necrotrophs produce symptoms related to the host's response.
Hemibiotrophy Definition
- Hemibiotrophy exhibits both biotrophic and necrotrophic phases, identified by temporal and spatial differentiation in pathogenic interactions, notably in species like Colletotrichum and Magnaporthe grisea.
Evaluation of Trophic Trisomy
- Biotrophy classification tends to capture many pathogens but leaves questions for intermediaries.
- Noted pathogens include Cladosporium fulvum and Phytophthora infestans, displaying specific feeding mechanisms like haustoria for nutrient extraction.
Limitations of Trophic Trisomy
- Viruses are classified separately due to their intracellular nature, while bacteria are known for wilting and vascular blockage.
Factors Influencing Biotrophs
- Require living host cells and are obligate in nature, with haustoria for nutrient uptake.
- Typically exhibit a narrow host range and utilize salicylic acid in defense mechanisms.
- Engage in gene-for-gene interactions involving virulent effectors.
Characteristics of Hemibiotrophs
- Start off feeding on living cells, transitioning to dead tissue, and are facultative.
- Possess haustorium-like structures; narrow host range; utilize both salicylic and jasmonic acid in defense.
- Feature avirulent effectors and qualitative resistance genes.
Key Traits of Necrotrophs
- Feed on dead or dying cells; facultative with no haustoria.
- Broad host range, utilizing jasmonic acid in defense, and possessing specific toxins and necrotrophic effectors.
- Resistance genes can exhibit quantitative traits.
Role of Effectors
- Effectors are pathogen-produced molecules influencing host interactions;
- Loss of virulence factors in biotrophs leads to pathogenicity confirmation.
- Necrotrophs deploy host-specific toxins to facilitate infection, while hemibiotrophs often possess virulence effectors, revealing complexity in pathogen-host interactions.
Shift in Pathogen Classification
- With advancements in genomic studies, traditional trophic classifications are being reevaluated, leading to a more nuanced understanding of pathogen categories.
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Description
Explore the classification of various fungal pathogens and their definitions. Learn about different strategies for combating plant diseases on a global scale, including biosecurity and agronomy. This quiz covers key concepts related to plant pathology and disease management.
