2013 Class: You are not responsible for the fungal endophytes of grasses or lichens questions below.
Plant Pathology
1. What is the difference between a symptom and a sign when referring to a plant disease caused by a fungus? What are some examples of symptoms? Of signs? Which is more likely to help you define the organism that caused the disease?
2. Are plant pathogens limited to a few fungal phyla? Explain your answer with examples.
3. What are some different ways that plant pathogens are dispersed? Does it vary depending on what type of disease the pathogen produces?
4. a. Explain the process, with details, of how one demonstrates that a fungus thought to cause a plant disease is responsible for that disease? What is the term that describes this process?
b. How is it possible that you may isolate a fungus from diseased plant tissue even though that fungus did not cause the disease?
5. Are fungal plant pathogens all closely related to each other? Give examples to explain your answer.
6. Why might some people say that fungal plant pathogens have more genes than saprobes? What barriers do plant pathogens have to overcome to reach their food source?
7. How do you use Koch's postulates when dealing with an obligate pathogen?
8. Why is it important to understand the infection cycle of a fungal pathogen when attempting to design a control strategy? What stages may be targets for control?
9. Are the rusty orange-colored pustules produced on the stems and leaves of wheat plants, by Puccinia graminis f.sp. tritici, due to teliospores or uredospores?
10. Do teliospores of Puccinia graminis f.sp. tritici initiate infection on any of its two hosts? Explain
11. Which spore stage(s) of wheat rust initiates infection on wheat and which stage(s) infects the Barberry plant?
12. Do you think eradication of the Barberry host could control the rust disease completely? Explain your answer.
13. Define:
Primary inoculum
Secondary inoculum
14. a. How did Phytophthora infestans get its name?
b. Why is the disease it causes considered historically significant, both in terms of its effect on humankind and on the field of Plant Pathology?
15. a. What are the signs and symptoms of late blight of potato?
b. What feature of P. infestans dispersal allows it to spread over much greater distances than most members of the Oomycota?
16. How has the worldwide spread of the second mating type strain of P. infestans (A2) led to new problems in late blight disease?
17. What are potential sources of disease inoculum for P. infestans? How are potato fields planted?
18. Define:
parasite
pathogen
necrotroph
biotroph
Fungi to know: Claviceps purpurea, Phytophtora infestans, Hemileia vastatrix, Magnaporthe oryzae Puccinia graminis f. sp. tritici, Ustilago maydis.
Lichens - A Fungal-Plant Relationship
1. In a lichen, what is a mycobiont and what is a photobiont?
b. Which one makes up the majority of the lichen structure?
c. For the photobiont, are they limited to a single kingdom? Explain.
d. Are the mycobionts all from a single phylum? Explain.
2. a. Do the lichen mycobionts represent a significant percent of the Ascomycota? Explain.
b. Do they represent unique genera in the Ascomycota? Explain.
b. What does the term "lichenized fungus" mean?
2. How are lichens named?
3. Photobionts have been shown to be capable of living on their own. What advantage(s) does the photobiont get by the association with the mycobiont?
4. What are the cortex and medulla layers in lichens and what role do they play in lichen biology?
5. Describe, using pictures if helpful, the differences between crustose, squamulose fruticose and foliose lichens.
6. Explain how lichens reproduce. How is this similar to fungal reproduction?
7. What is a soredium? What part does it have in lichen reproduction? Is this sexual or asexual?
8. How do lichens live in conditions in which other plants cannot?
9. a. Explain why some consider the lichen relationship to be mutualistic, while others consider it to be controlled parasitism.
b. What do each partner in the relationship get from the other?
7a. What are some of the economic uses for lichens?
b. Why are lichens of potential interest for treating human diseases?
8. Why are lichens good indicators of pollution?
Fungal Endophytes of Grasses
1. What exactly is an endophyte? How do you think this class of organisms got that name?
2. Two types of endophytes were discussed, the Class I endophytes of grasses Claviceptaceous (C-endophytes) and the non-Claviceptaceous (non-C) type endophytes?
a. What is the difference between them in terms of host-specificity?
b. How do they differ in how they are transmitted from generation to generation in plants?
c. How do they differ in their diversity within a single plant (or even a single leaf)?
3. What benefits do fungal endophytes provide to grasses?
b. Do they cause some deleterious effects on the grasses? What are they?
4. How do endophytes in grasses cause problems for cattle?
5. What potential roles do Class 3 (non-C) endophytes play in the interaction with their plant host? Is this clearly understood?
6. How does the interaction between a fungal endophyte and its host plant differ from that of a fungal pathogen differ and its host?
7. When purifying fungal endophytes, what do you do to avoid isolating fungi that just happened to land on a plant surface?