Abstract
Sheath blight (Rhizoctonia solani) causes severe loss in the production of rice in India. Twenty five (25) isolates were collected from different parts of India. Morphological and cultural characters were investigated, on the basis of colony colour, growth pattern, hyphal width, colony growth, formation of sclerotia, size of sclerotia, diameter and number of sclerotia. Pathogenic variability was studied on highly susceptible cultivar Pusa Basmati-1 and isolates were classified into two major groups that is, highly virulent and virulent. Genetic variability of R. solani was also analyzed using 10 RAPD markers and on the basis of Jaccard’s similarity coefficient, 4 major clusters were formed. The range of genetic similarity varied from 17 - 77%. Maximum similarity (77%) was found between two isolates (RS-14 and RS-15) both from Kerala whereas, lowest similarity (17%) was observed between RS-22 (Delhi) and RS-4 (Punjab). Isolates from same geographical regions showed similarity in DNA profiles except few isolates from Uttar Pradesh and Punjab. Isolates were classified based on morphological, cultural characters and some isolates were identified as highly virulent and virulent.
Key words: Rice, sheath blight, Rhizoctonia solani, cultural, pathogenic, molecular, variability.
