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Subject: Plant Pathology × End date: 2018 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Epidemiology and integrated management of potato wilt caused by sclerotium rolfsii sacc.
    (UAS Dharwad, 2007) Venkatesh R.Kulkarni; Yashoda R.Hegde
    The sclerotium wilt /rot caused by Sclerotium rolfsii Sacc. is one of the major soil borne diseases of potato causing heavy losses every year. The incidence of wilt was noticed in all locations surveyed with a range of 1.50 to 12.40 per cent and incidence of rot ranged from 2.00 to 16.25 per cent. The maximum incidence of wilt was noticed in Belgaum (7.25%) and least in Bidar (2.50) districts. The rot incidence was more in Dharwad (9.51%) less in Bidar (5.72%) districts. Four per cent inoculum level was sufficient to cause 100 per cent infection. The maximum per cent germination of sclerotium (87.50%) was noticed at 1 cm depth, which gradually reduced with increase in depth. The germination of sclerotium was 100 per cent up to one month after storage and decreased gradually with increase in storage duration. The rate of movement of mycelia at low inoculum level (one sclerotium) took eight days to cover 9 cm distance, but higher inoculum (five sclerotia) took 6 days to reach the same. Colonization of sorghum seeds and germination of sclerotia were drastically reduced with increase in EC levels. Growth of the pathogen was maximum at the temperature of 25-300C, soil moisture of 30 per cent and pH of 5.5 to 9.0. The results of morphological and cultural studies indicated that there was slight variation among ten isolates. RAPD data distinguished isolates in to two major clusters A and B. The results revealed that, geographical locations of isolates were closely related. All 12 hosts were found susceptible. Among 63 genotypes screened only 3 genotypes showed less than 4 per cent incidence. IDM experiments conducted in farmers fields revealed that, maximum suppression of the disease was observed when carboxin (2g kg-1) and Trichoderma harzianum were used for tuber treatment and supplemented with either FYM or vermicompost. The highest total return and additional return over control were obtained in carboxin + T. harzianum + FYM treatment. There was a gradual increase in population of both T. harzianum and T. viride over the two years in all locations. The competitive saprophytic ability (CSA) of pathogen was found to decrease over the years. The B: C ratio of IDM trials in farmer’s fields showed above 3 for both the years in all the locations.