Question

Bakanae disease was due to
A. Fungi toxin
B. Growth hormones released by fungal infection
C. Inadequate nutrients
D. Change in photoperiods

Answer 1

Hint:- The earliest known case of bakanae disease was in 1828 and it was first described scientifically in 1898 by Japanese researcher Shotaro Hori, who demonstrated that the causative agent was fungal in nature. The fungus affects rice crops of various places including Asia, Africa, and North America. In epidemic conditions, yield upto 20% or more is lost.

Complete Answer:- Bakanae disease is caused by the fungus, Gibberella fujikuroi that infects rice plants. The metabolism of the fungi produces gibberellic acid in the plant, which being a growth hormone causes hypertrophy. The pathogen is present in the seed and soil.
The infected plants are highly etiolated, chlorotic in nature and infertile thus producing no edible grains. They are incapable of supporting their own weight and thus die. However, the seedlings appear whitish, pale and weak and the tips show wilting in severe conditions.
Bakanae disease is also called foolish seedling disease as these infected plants flower earlier (because of the gibberellin hormone production inside the plant). The diseased plants are often conspicuous in a field because of their extreme height and spindly appearance. These plants are unable to support themselves and have sterile male reproductive systems. The plants die in about 2 weeks to 2 months after the infection.
Thus, the correct answer is option B.

Note:- The disease can be controlled by taking preventive measures such as the seeds must be collected from areas free from the disease, storage of seeds should be done in dry conditions and the use of fungicides like topsin or benlate. The use of excess nitrogen fertilizers and moisture predisposes the rice plant to the fungal attack.