Plant Pathology Module 2

1. The term epiphytotic is used for a widespread plant disease outbreak.
2. Zoospores are motile spores found in Oomycetes and Chytridiomycetes.
3. Late blight of potato was the cause of the Irish Famine (1845-1847).
4. Biological control means managing disease using living organisms like antagonistic fungi or bacteria.
5. Trichoderma harzianum is used as a biocontrol agent against soil-borne pathogens.
6. Agrobacterium tumefaciens causes Crown gall disease in dicots.
7. The Ti-plasmid of Agrobacterium is used in genetic engineering.
8. Mosaic symptoms are due to virus infection.
9. Wilt diseases are mainly caused by Fusarium and Verticillium
10. Smuts replace grain with black masses of spores (e.g., Ustilago species).
11. Rust fungi (Puccinia spp.) require two hosts — they are heteroecious.
12. Teliospores are the resting spores of rusts and smuts.
13. Downy mildew affects crops like bajra, maize, and grapes.
14. Powdery mildew thrives in dry conditions, unlike downy mildew.
15. Ergot of bajra produces alkaloids toxic to humans and animals.
16. Red rot of sugarcane is caused by Colletotrichum falcatum.
17. Loose smut of wheat is internally seed-borne.
18. Covered smut is externally seed-borne.
19. Seed treatment with fungicides like carbendazim or thiram helps control seed-borne diseases.
20. Bacterial blight of rice is caused by Xanthomonas oryzae pv. oryzae.
21. Tundu disease of wheat is caused by Anguina tritici (nematode) and Corynebacterium tritici (bacterium).
22. Mosaic diseases show light and dark green mottling on leaves.
23. Ring spot symptoms are common in Papaya Ring Spot Virus (PRSV).
24. Tobacco mosaic virus (TMV) was the first virus discovered (1892).
25. Viroids are naked RNA molecules without protein coats.
26. Mycoplasma-like organisms (MLOs) cause phyllody and little leaf diseases.
27. Phyllody means flowers turning into leafy structures.
28. Phytoplasmas are transmitted by leafhoppers and planthoppers.
29. Soft rot bacteria produce pectinases that break down plant tissues.
30. Galls are abnormal outgrowths due to pathogen infection or insect attack.
31. Sclerotia are hard resting bodies formed by fungi like Sclerotium rolfsii.
32. Damping-off affects seedlings and is caused by Pythium and Rhizoctonia.
33. Wilt occurs due to xylem blockage caused by pathogen growth.
34. Leaf spots can be caused by fungi, bacteria, or viruses.
35. Anthracnose results in dark, sunken lesions on fruits and stems.
36. Blight causes sudden death of tissue, affecting large areas of the plant.
37. Dieback starts from the tip of the branch and progresses downward.
38. Yellowing and chlorosis occur due to virus or nutrient deficiency.
39. Systemic infection spreads throughout the plant.
40. Localized infection remains confined to a small area.
41. Penetration of pathogens occurs via natural openings or wounds.
42. Enzymes like cellulase and pectinase help pathogens penetrate host tissues.
43. Toxins like tabtoxin, victorin, and phaseotoxin are produced by fungi.
44. Phytotoxins affect specific plant species.
45. Resistance is the plant’s ability to restrict pathogen development.
46. Susceptibility is the inability to resist pathogen invasion.
47. R-gene in plants confers resistance to specific pathogens.
48. Hypersensitive response (HR) is a localized cell death to prevent pathogen spread.
49. Systemic Acquired Resistance (SAR) is a whole-plant defense mechanism.
50. Host–Pathogen Interaction follows the gene-for-gene hypothesis proposed by Flor (1956).
51. Gene-for-gene hypothesis was proposed by H. H. Flor (1956) while studying flax–flax rust interaction.
52. Tabtoxin is a non-host specific toxin produced by Pseudomonas tabaci.
53. Victorin is a host-specific toxin produced by Helminthosporium victoriae (oat blight).
54. T-toxin is produced by Helminthosporium maydis race T, causing southern corn leaf blight.
55. Phaseotoxin is produced by Pseudomonas phaseolicola in halo blight of bean.
56. Fusaric acid is a toxin secreted by Fusarium oxysporum.
57. Thaxtomin is produced by Streptomyces scabies, causing common scab of potato.
58. Coronatine is produced by Pseudomonas syringae, which induces chlorosis.
59. Helminthosporoside is produced by Helminthosporium oryzae in brown spot of rice.
60. Cercosporin is produced by Cercospora spp. causing leaf spot diseases.