Question

Which one causes Blight disease of rice?
(a) Xanthomonas oryzae
(b) Pseudomonas oryzae
(c) Erwinia oryzae
(d) Corynebacterium oryzae

Answer 1

Hint: This is a species of Proteobacteria. The major host of the bacterium is rice. The species contains two types of pathogens which are not European. In severe epidemics, crop loss may be as high as $75\%$, and millions of hectares of rice are infected annually.

Correct step by step Answer:
Blight disease of Rice is a deadly disease that affects the cultivated rice in a field and is easily transmitted to other crops also.. It is caused by bacteria Xanthomonas oryzae. It causes drooping of seedlings and yellowing and drying of leaves. Thus, the correct answer is 'Xanthomonas oryzae.'
So, the correct answer is, ‘Xanthomonas oryzae.’

Additional Information: Methods of controlling rice bacterial blight are of limited effectiveness. Chemical control has been largely ineffective in minimizing bacterial blight due to safety concerns, practicality, and bacterial resistance. Biological control methods, which believe the utilization of bacterial antagonists of pathogens (disease- causing organisms) , can reduce bacterial blight, though their use has been limited. The most common method of defending against rice bacterial blight is the cultivation of rice varieties by making them disease resistance, by the addition of resistant genes. Over 30 resistance genes, termed Xa1 to Xa33, are identified in rice plants, and some, like Xa21, are some others are integrated into the genomes of economic rice strains. These resistant rice varieties are largely successful, dramatically reducing yield losses in many rice- producing countries.

Note: It is transmitted during rain splashes including wind injuries to rice leaves, irrigation water.
Damage symptoms:
- The $5-10 \ mm$ long green-yellow spot at the tip of the leaves.
- These spots enlarge and turn to yellow.
- It begins as water-soaked stripes on the blade.
- A drop of bacterial exudates could also be observed on young lesions.