Both rice and wheat are hosts of Rhizoctonia solani Kuhn. It is responsible for sheath blight, one of the most important diseases, in rice in U.P. Tarai, whereas its infection in wheat is yet to be recorded in the same area. Wheat as a previous crop does not favour sheath blight in rice. Present investigation has been undertaken to explore this behaviour. When inoculated inside the sheath, most of the 48 rice isolates of R. solani induced typical sheath blight in both rice and wheat. In wheat three isolates even infected glumes. However, unlike rice sheath blight lesions in wheat were restricted to inoculated sheath only and did not spread to other sheaths. Interestingly, when mixed with soil most of the isolates of R. solani infected rice sheath but not wheat. Five isolates induced stunting in wheat seedlings. When inoculum was placed at the base of the wheat seedlings three isolates induced sheath blight symptoms in lower sheaths that were in contact with soil. In field, sheath blight could be induced in rice by artificial inoculation any time during the cropping season. However, in wheat only inoculations done after February were successful. Reasons for the inability of R.solani to attack wheat under natural condition of U.P. Tarai are: (i) absence of flooding during wheal crop season due to which inoculum is unable to come in contact with infection court (i.e. inner sheath surface), (ii) non-overlapping sheaths resulting in non-spread of disease from infected to other sheaths and (iii) unfavourable climatic conditions.

Research and Partnership Program

English

0201|R02JOURN|AL-Economic Program|AL-ABC Program|3

Maria del Carmen Nava

INT1237

CIMMYT Staff Publications Collection