Part I. T or F. If false, explain why. Use an example. (20 pts.)
1) Indicator plants used to detect plant viruses are always inoculated by rubbing infective sap on the leaves.
2) All plant pathogens are parasites.
3) Wind is always an important factor in the dissemination of fungal spores.
4) Angular leaf spots are a common symptom of bacterial infection.
5) Sclerotia are produced only by Ascomycetes.
6) All plant pathogenic prokaryotes can be grown in culture.
7) Micronutrient deficiencies can often be corrected by adjusting soil pH.
8) All plant pathogens produce toxins and enzymes that degrade plant cells.
9) Stunting is a common symptom of nematode injury.
10) Powdery mildew fungi remain on the leaf surface, so they should not really be called parasites.
Part II. Match the correct genus name. 10 pts.
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Venturia
Pythium
Striga
Agrobacterium
Meloidogyne
Botrytis
Aspergillus
Verticillium
Pseudomonas
Alternaria
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1) Root-knot nematode
2) Vascular wilt fungus
3) Includes soft-rot bacteria
4) Apple scab
5) Most common cause of damping-off
6) Conidia with alternating horizontal and vertical septa
7) Crown gall
8) Gray mold disease
9) Produces aflatoxin
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Part III. Write the correct term 10 pts.
1) closed sexual fruiting body of powdery mildew fungi
2) the “exogenous dormancy” that keeps spores from germinating too soon
3) pleomorphic mollicute
4) full scientific name (genus and species) name for a xylem-limited fastidious bacterium
5) feeding structure of a nematode
6) Gram+ genus of plant pathogenic bacteria
7) The person who first proved that a fungus caused a plant disease following the Irish potato famine
8) Sexual spores of Oomycetes
9) Structure on mycelium that is found only in Basidiomycetes
10) Thick-walled asexual spore
Part IV. Short answers. 40 pts.
1) Name 6 survival spores or structures produced by plant pathogenic fungi (3 pts.).
2) Name one secondary air pollutant and its source (2 pts.)
3) What are 2 ways that bacterial diseases are different from most fungal diseases of plants? (2 pts.)
4) Choose a plant pathogenic Oomycete, Ascomycete, and Basidiomycete and fill in the chart:
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Survival structure |
Mycelial characteristics |
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5) Why has fungicide resistance become a significant problem only since the late 1970s?
6) Name 3 alternatives to chemical control for nematodes. Discuss briefly, a limitation to the use of each. (6 pts.)
7) Briefly, describe how the knowledge of whether a pathogen is a monocyclic or a polycyclic pathogen can help in the design of an effective disease management program. (3 pts.)
8) You have been given a stunted plant. What are 3 possible pathogen causes of this symptom, and how can you determine which one is the causal agent? (6 pts.)
9) What are 2 symptoms that suggest an abiotic problem rather than a biotic one? (4 pts.)
10) What are 2 features of Oomycetes that exclude them from the true Fungi? (4 pts.)
11) Describe one successful example of a plant disease biological control and why it works. (2 pts.)
Part V. Final essay. Choose only one. 20 pts.
Many people in the general public would like to see “chemical” pesticides banned and replaced with biological controls. Discuss some of the advantages and disadvantages of both chemical and biological disease management. How do you think that plant disease management, in general, should be optimized in this new century?
OR
Describe the basic biology of the major groups of plant pathogens and what adaptations they have made to become parasites of plants. Consider, for example, survival, dispersal and infection.
