Rice is a staple food for human being all over the world and India is the second largest producer and consumer of rice at global level. Production of rice in India is limited by several biotic and abiotic factors. Rice sheath blight (Rhizoctonia solani AG1-IA) is one of the most important factor causes significant grain yield and quality losses at worldwide. Yield losses of up to 50% have been reported under most conducive environments in India. Several uncultivated (weeds) and cultivated plant species are known to act as alternate and collateral hosts of R. solani in different agro-climatic regions of India. The cv. Pusa Basmati-1 (PB-1) grown in the western plain region of Uttar Pradesh and to screen weed species growing in and around paddy fields to study the carryover of pathogen from rice to weeds and vice-versa. Out of 75 weed species tested for host range of R. solani, 73 were found to show high or low degree of symptoms in vitro. Whereas, 11 weed species i.e. Launaea procumbens, Cynodon dactylon, Echinochloa colona, Blumea lacera, Eragrostis tenella, Typha angustata, Chloris barbata, Xanthium strumarium, Cyperus rotundus, Paspalum distichum and Bidens pilosa were found to carry infection of R. solani as they exhibited characteristic symptoms after artificial inoculation. A total of 22 weed species were evaluated inside rice field using cv. PB-1 to know infection level and how associated in spreading the disease. Out of 22 weed species, 13 weed species viz. Echinochloa colona, Brachiaria decumbens, Cyperus rotundus, Setaria verticillata, Paspalum distichum, Leptochloa chinensis, Brachiaria reptans, Imperata cylindrica, Saccharum spontaneum, Digitaria sangunalis, Cyperus difformis, Eclipta alba and Cynodon dactylon showed higher disease incidence and five weed species i.e. Sorghum halepense, Echinochloa colona, Paspalum distichum, Imperata cylindrica and Desmostachya bipinnata were showed higher disease severity as well as a very prominent role in spreading R. solani to rice plants during both the years (2011 and 2012). Weed species Echinochloa colana and Brachiaria decumbens associated with rice were maximum percent disease severity (15.62% & 12.33%) and disease incidence (25.47% & 24.41 %), respectively when planted in between the rows of rice under field condition. These weeds are having played a crucial role in transfer and spread of pathogen from weeds to rice crop. These studies will help in managing the sheath blight disease.

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