Effect of Botanical Extracts: A Potential Biocontrol Agent for Xanthomonas Oryzae Pv. Oryzae, Causing Bacterial Leaf Blight Disease of Rice

Research in world rice production.This important crop badly suffers from more than forty different microbial disease and disorders.Among them, bacterial leaf blight of rice (BLB) caused by Xanthomonas oryzae pv.oryzae (Swings et al., 1990) is a serious threat for irrigated, deep water, rainfed, temperate, tropical and subtropical rice growing areas of the world (Mew, 1987).This destructive disease has now become a serious pathosystem to rice crop especially in South East Abstract | Bacterial leaf blight is a devastating disease of paddy rice crop throughout the rice growing countries.Several commonly available plant decoctions were investigated as the bioactive eco-friendly compounds, and as the possible alternatives to hazardous chemicals for the control of BLB of rice.Aqueous extracts of fifteen different plant parts either individually or in combination were tested at various concentrations under in vitro conditions by poison food and disk diffusion techniques while best effective seven were trialed in glass house and field experiments to determine their efficacy against Xanthomonas oryzae pv.oryzae.In vitro and in vivo studies under different conditions showed significant response of Mentha piperita, Azadirachta indica and Aloe vera either tested individually or in combination of two or more than two decoctions against the bacterium in question.When used individually, M. piperita demonstrated best in vitro, field and glass house experiments followed by the A. indica which also proved its efficacy against the pathogen.The combination of M. piperita, A. indica and C. limon was superior in reducing the BLB of rice.Besides this, all treatments showed significant effect on the agronomic traits of rice plants.The reduction of disease in all the trials along with healthy crop stand in glass house and field indicated that these decoctions might play an important role in biological management strategies for the control of BLB of rice.The present research may provide an avenue for the formulation of new bactericides for future uses.