Question

Black rot of mustard is caused by
A. Colletotrichum falcatum
B. Xanthomonas oryzae
C. Xanthomonas campestris
D. Phytophthora infestans

Answer 1

Hint: Black rot kills cabbage worldwide and related crops (mustard, radish) and is caused by the Xanthomonas campestris pv. campestris (Xcc), a type of bacteria. In hotter weather, black rot is among the most severe cabbage/kale diseases.

Complete answer:
Black rot, produced by infection (Xcc), is regarded as the crucifer's main significant and perhaps most devastating disease, infecting all grown brassica varieties internationally. It's since been found almost in every nation where crop brassicas are produced annually. At a certain stage of the life cycle of plants, host colonization by Xcc might occur. V-shaped chlorotic to necrotic lesions expanding from the leaf margins and blackening of vascular tissues are characteristic symptoms of dark rot caused by Xcc. The legal route of the Xcc invasion will be through the hydathodes, whereas insect- and plant-roots-induced leaf wounds may also be entry points. Rarely, infections occur through stomata. Hydathodes just provide pathogens with a solid objective to the plant vascular system from the lower leaves and thus to systematic host invasion. Suture vein invasion supports the development of seeds corrupted with Xcc. Xcc can live for up to two years in plant residues in the soil, and not more than six weeks in free soil. As a source of additional inoculation, bacteria present in the plant debris might serve.

So, the correct option is C.

Note: When warm, humid conditions follow intervals of rainy weather during initial crop production, the infections can affect the major loss of yield. Late infections can give certain rotting species a gap to enter and inflict substantial damage during preservation. Obviously, it depends on the host, cultivar, planting date, and environmental conditions, manifestations of black rot vary considerably.