Epidemiology and integrated management of potato wilt caused by sclerotium rolfsii sacc

Abstract

The sclerotium wilt /rot caused by Sclerotium rolfsii Sacc. is one of the major soil newlineborne diseases of potato causing heavy losses every year. The incidence of wilt was noticed newlinein all locations surveyed with a range of 1.50 to 12.40 per cent and incidence of rot ranged newlinefrom 2.00 to 16.25 per cent. The maximum incidence of wilt was noticed in Belgaum (7.25%) newlineand least in Bidar (2.50) districts. The rot incidence was more in Dharwad (9.51%) less in newlineBidar (5.72%) districts. newlineFour per cent inoculum level was sufficient to cause 100 per cent infection. The newlinemaximum per cent germination of sclerotium (87.50%) was noticed at 1 cm depth, which newlinegradually reduced with increase in depth. The germination of sclerotium was 100 per cent up newlineto one month after storage and decreased gradually with increase in storage duration. The newlinerate of movement of mycelia at low inoculum level (one sclerotium) took eight days to cover 9 newlinecm distance, but higher inoculum (five sclerotia) took 6 days to reach the same. Colonization newlineof sorghum seeds and germination of sclerotia were drastically reduced with increase in EC newlinelevels. Growth of the pathogen was maximum at the temperature of 25-300C, soil moisture of newline30 per cent and pH of 5.5 to 9.0. newlineThe results of morphological and cultural studies indicated that there was slight newlinevariation among ten isolates. RAPD data distinguished isolates in to two major clusters A and newlineB. The results revealed that, geographical locations of isolates were closely related. All 12 newlinehosts were found susceptible. Among 63 genotypes screened only 3 genotypes showed less newlinethan 4 per cent incidence. newlineIDM experiments conducted in farmers fields revealed that, maximum suppression of newlinethe disease was observed when carboxin (2g kg-1) and Trichoderma harzianum were used for newlinetuber treatment and supplemented with either FYM or vermicompost. The highest total return newlineand additional return over control were obtained in carboxin + T. harzianum + FYM treatment. newlineThere was a gradual increase in population of both T. harzianum and T. viride ove