DISEASE REACTION OF POTATO GERMPLASMS AND TRUE POTATO SEEDS AGAINST RHIZOCTONIA SOLANI KUHN

Screening of 25 potato germplasms against Rhizoctonia solani BTB115 in artificially infested field condition were carried out. No germplasm was found resistant to R. solani. Only six germplasms appeared to be moderately resistant. Cardinal, Diamant and Heera were found as highly susceptible varieties. True potato seed BARI TPS1 was tested against two virulent isolates of R. solani DK64 and BTB115. Only 21 % and 29 % resistant seedlings against the DK64 and BTB115 isolates, respectively were obtained compared to 85% seedlings in control. Susceptibility of potato to 55 diseases has been recorded in Bangladesh (Ali and Dey 1994). Stem canker and black scurf caused by Rhizoctonia solani Kuhn is one of the most destructive diseases of potato. The incidence of three diseases in Bangladesh is 8.40 % (Khandaker et al. 2006). Loss caused by R. solani were estimated to 5-15 % world-wide (Stachiwicz et al. 1978). The fungus is an unspecialized parasite, survive in soil in the absence of host plant and make itself a very difficult pathogen to manage. Cultivation of resistant varieties is the most economic and environmentally safe method of crop disease management. But availability of resistant genotypes is reported to be very limited