Biological Management of Bacterial Leaf Blight of Rice (Xanthomonas oryzae pv. oryzae) through Rice Rhizosphere Antagonist Actinobacteria

Rice (Oryza sativa L.) is a staple food crop for more than two billion people around the world. Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) (Ishimiya) Swings et al. is one of the most destructive diseases of rice in all the major rice-growing. Use of antibiotics is the common practice for the management of BLB, but it has detrimental effect on human health and environment. Hence other eco-friendly strategies like biological control and host plant resistance (HPR) should be effectively exploited for BLB management. An attempt was made to manage the disease using actinobacteria isolated from rice rhizosphere. Among sixteen actinobacterial isolates, six were selected for secondary screening based on disc diffusion assay. Out of six isolates AUDT-502 produced maximum zone of inhibition (1.81 cm) followed by AUDT-508 (1.62 cm) and were evaluated under glasshouse condition. AUDT-502 (Streptomyces rimosus) appeared as the most promising bio agent which was able to inhibit the pathogen (Xoo) both in in vitro and in vivo condition. AUDT-502 increased the plant growth parameters like number of tillers (5.73), plant height (56.85 cm), root length (34.33cm) and dry root weight (3.90g) and also reduced the leaf blight lesion length and per cent disease index (4.43 per cent) significantly when compared to other treatments. The current study thus showed that there was a good correlation between in vitro inhibition of the pathogen and the in vivo control of the disease and AUDT-502 (Streptomyces rimosus) appears to be a hopeful bioagent for the management of bacterial leaf blight of rice.