A plant disease which is not caused by a fungus is
A. Red rot of sugarcane
B. Late blight of potato
C. Black rot of crucifers
D. Brown rust of wheat

Hint:The condition is also called blight, black stem, black vein, stem rot, and stump rot. It is the most widespread and damaging disease of the cabbage family.

Complete Answer:
Generally, a plant becomes diseased when it is continually affected by a causal agent that results in an irregular physiological process that deeply affects plant development, work, or other behaviour. Plant diseases may be broadly categorised according to the existence of their main causal agent, either infectious or non-infectious. Infectious plant diseases are caused by pathogenic agents or parasitic flowering plants. Non-infectious plant diseases are caused by unfavorable growth conditions, including high temperatures, detrimental interactions between moisture and oxygen, harmful contaminants in soil or environment, and abundance or lack of essential minerals.

Red rot disease is caused by the Colletotrichumfalcatum fungus. The signs of the disease are the reddening of the internal internodal tissues with white patch crossbars in the reddish region. The late blight of Potato is caused by the Phytophthora fungus. It infects and kills the leaves, roots, fruit and tubers of potato and tomato plants. Black crucifer rot is caused by the bacterium Xanthomonascampestris. The outcome is a dark brown discoloration of fruit and vegetables stems. Wheat leaf rust is a disease caused by Pucciniatriticina fungus. This rust disease happens where maize, barley and other cereal crops are cultivated.

Thus, the correct answer is A i.e., Black rot of crucifers.

Note:Black rot symptoms might not occur until more than a month after cruciferous crops begin to grow. The early signs are odd, dull, yellow blotches on the edges of the leaves.