Biological Classification Question 91
91. Which one is the wrong pairing for the disease and its causal organism?
(a) Black rust of wheat - Puccinia graminis
(b) Loose smut of wheat - Ustilago muda
(c) Root-knot of vegetables - Meloidogyne sp
(d) Late blight of potato - Alternaria solani
Show Answer
Answer : d
Hints & Solutions
(d) Late blight is caused by the fungus Phytophthora infestans. Late blight appears on potato or tomato leaves as pale green, watersoaked spots, often beginning at leaftips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire veins may be killed in a short time when moist weather persists.
