Epidemiology of Bacterial Leaf Streak of Rice

Abstract

Studies were conducted on the perpetuation and host range of the rice leaf streak pathogen Xanthomonas translucens f. sp. oryzae (Fang et al.) Pordesimo (=X. oryzicola Fang et al.) and the factors affecting the disease.Seeds from a diseased crop when sown newt season, developed diseased seedlings under field as well as laboratory conditions. The bacterium was isolated from these seedlings and its pathogenicity was confirmed. No diagnostic symptom attributable to bacterial infection was detected on such seeds, nor the bacterium could be isolated. The bacterium did not perpetuate in infected debris. Even in the leaves and bacterial beads stored under room conditions, the bacterium remainedviable upto 90 and 75 days respectively. The bacterium did not infect any of the 30 grasses, 8 cereals and millets including maize and 4 species of Cyperus.The young rice leaves were more susceptible to the disease, and became resistant with age. Two to three continuous days with high humidity (R.H. 83.0-89.5%) or dew during morning hours were necessary for infection. The lesion enlargement was favoured by moderate temperatures (26.1-30.5°C) and retarded at lower range (below 22.4°C), irrespective of relative humidity.