Bacterial blight of rice.PPTXRice bacterial blight is one of the deadly bacterial diseases, which is the most destructive affliction of cultivated rice (Oryzae sativa and O. glaberrima).

Rice bacterial blight is one of the deadly bacterial diseases, which is the most destructive affliction of cultivated rice (Oryzae sativa and O. glaberrima).

1. Bacterial Blight of Rice Pragya Atrey Department of Microbiology

2. Rice bacterial blight is one of the deadly bacterial diseases, which is the most destructive affliction of cultivated rice ( Oryzae sativa and O. glaberrima). It is also known as the bacterial blight of rice. Bacterial leaf blight of rice is caused by a species of Xanthomonas . It is an aerobic, rod shaped, non-capsulated, non-spore forming, gram-negative bacterium . It is motile with single polar flagellum. It produce waxy yellow color colonies on agar medium . This disease was first found in Kyushu, Japan (1884 - 1885), and the causal agent like bacterium Xanthomonas oryzae was first identified in 1911 at that time, this was named Bacillus oryzae

3. Symptoms : When the disease affects a seedling of the rice plant, the infected leaves first turn yellow to straw colored, and later it would wilt and die and in mature rice plants, it mainly occurs from tillering to panicle formation . Primarily the plant is light green to greyish green and water-soaked streaks appear on the leaves but once the bacterial blight affects it, they form larger yellowish lesions with uneven edges . Further, the leaves become yellow, gradually wilt and die . In the final stage of the bacterial blight, a milky bacterial ooze is observed dripping from the leaves, this can be left to dry finally a white crust can be observed

4. Favorable Conditions for Bacterial Leaf Blight of Rice : Occurs mostly in irrigated and rained lowlands. The temperature of 25 – 34°C, Relative Humidity above 70%, high nitrogen fertilization, strong winds and continuous rainfall are favorable conditions for disease infection.

5. Method of Controlling Rice Blight There are methods to control rice blight: biological control and chemical control . Biological Control - Until today there is no biological product, available commercially to control bacterial rice blight. But there are some of the products based on copper that would help to reduce the symptoms but cannot control the disease . Chemical Method - To fight against bacterial blight, rice seeds are treated with authorized antibiotics with copper oxychloride or copper sulphate has been recommended. In some of the countries the use of antibiotics is prohibited, So go through your country guidelines before using them .

6. Preventive Measures of Bacterial Blight Some of the preventive measures taken to prevent bacterial blight of paddy (rice) are : • It can be prevented by using healthy seeds, like from a certified source. • Bacterial blight-resistant rice varieties, it is one of the most effective and reliable ways to control diseases, and it is one of the cheapest ways of prevention. • By properly handling the seedlings during transplanting. • By properly adjusting the nitrogen fertilizers and by applying the extra dose of potash along with the last dose of nitrogen, when weather conditions are favourable . • By avoiding the use of nitrogen in the form of urea. • By removing a weed and other hosts from the rice field and by ploughing under rice stubble, straw, ratoons, and volunteer seedlings can serve as hosts for the bacteria . • Leave the land uncultivated in between the season to suppress the disease agents in the soil and plant residues.

7. Disease cycle : • It is principally a vesicular disease. • Seeds and disease stubbles are mainly the primary sources of infection. • The secondary infection spreads due to wind-borne rain splashes and gains entry into the host through wounds and stomata. • High doses of nitrate, silicate and magnesium in the soil

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