Question

Citrus canker is caused by
A. Lactobacillus bacteria
B. Xanthomonas bacteria
C. Anthrax
D. None of the above

Answer 1

Hint: Citrus canker is a disease caused by pathogenic bacterial species that enters through the stomata of leaves or by cuts on plants. It usually affects citrus plants like orange and lemon. The infected plants develop blister-like lesions on its fruits and leaves. These lesions then turn the leaves or fruit black or brown in color.

Complete step by step answer: The citrus canker disease is a very persistent plant disease. It is believed to have emerged from regions of South –Asia. Once it infects the plants it is very difficult to reverse it. The bacterium enters the plant through wounds or cuts on the leaves or stems. Generally, the infection occurs through the entry of bacterium through the stomata of the leaves. The gram-negative rod-shaped bacteria named Xanthomonas citri is the causative agent of citrus canker. It infects the fruits and makes them undesirable in appearance making them inappropriate to be sold. Although infected fruits can be eaten safely, they are not desirable to be sold. The blister-like lesions are surrounded by yellowish fluid. The bacterial spores ooze out of these lesions and spread through wind or rain to other plants. The bacteria stick to the plants by forming a biofilm. This biofilm then leads to the production of extracellular polysaccharides that further helps in the entry of bacteria inside the plant cells.
Thus, Xanthomonas species that causes citrus canker. So, the right answer is option B.

Note: The citrus canker possesses a great threat to citrus fields. It is very hard to control this disease once it infects even a single plant in the field. The only possible measures of control include sanitation and quarantine practices of plants.