Question

Loose smut of wheat is caused by
A) Ustilago nuda
B) Crystopus tritici
C) Puccinia graminis
D) Aspergillus graminis

Answer 1

Hint:Loose smut has a wide range and can occur anywhere wheat is processed. Inside the embryo of an infected wheat seed, the fungus causing loose smut persists as dormant mycelia.

Complete answer:
The fungus Ustilago tritici is caused by it. Prior to heading, mild symptoms may be present, including yellowish leaf streaks and stiff, dark green leaves. Affected plants head out early, producing sterile heads in place of healthy glumes and kernels with clumped, sooty olive-black spores. Spores are not enclosed by the seed coat, so after emergence, they are quickly dispersed by rain or wind. Only a bare rachis remains with a few fragments of glum or awns after the spores disperse.

The fungus becomes active again when the seed germinates. Within the growth point, the fungus develops and moves into the developing grain tissue as the wheat plants grow.

When the head emerges, instead of flowering portions, there are masses of black spores on the spikelets
When flowering, these spores infect other wheat plants, causing seed infection. Seeds that have been infected appear healthy. After heading, the best time to scout is. Affected plants head out early, producing sterile heads instead of healthy glumes and kernels with clumped, sooty olive-black spores. The fungus is seedborne, and no disease will occur in a field unless infected seeds are planted. New infections during flowering are favoured by humid, cool weather of 60-72 degree Farenheit. Less susceptible wheat varieties are available.

Thus the correct answer is option (A) Ustilago nuda.

Note:In order to reduce disease risk, plant certified seeds. Do not save seeds from loose-smut fields. Treatments with fungicide seeds can manage loose smut effectively.