STUDIES ON VARIABILITY AND PATHOGENICITY OF Ralstonia solanacearum (Smith) ISOLATES CAUSING WILT OF TOMATO (Mill)
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Date
2015-08
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bengaluru).
Abstract
Field survey in major tomato growing areas of Karnataka revealed that the incidence of bacterial wilt varied with different zones of Karnataka. Highest disease incidence in tomato was recorded in Haasan (19.6 per cent) followed by Chikkamagalur (16.1 per cent), Bengaluru rural (12.7 per cent) and Chikkaballapur (5.21 per cent) districts of Karnataka. A total of 38 isolates collected were tested for their biovar pattern. All the 38 isolates of Ralstonia solanacearum utilized and oxidized the sugar alcohols and disaccharides, thus, indicating that all the 38 isolates belonged to biovar III. Interaction between Meloidogyne incognita and Ralstonia solanacearum clearly indicating that inoculation of M. incognita, 10 days prior to the inoculation of R. solanacearum led to maximum wilt incidence (100 per cent) followed by combined inoculation of both the pathogens (66.66 per cent). The efficacy of different bioagents in managing the wilt complex revealed that treatment with consortia of Trichoderma viride [10 g per pot (2×106 cfu / ml)] + Pseudomonas fluorescens [10 g per pot (2×108 cfu / ml)] + Verticillium chlamydosporium [10 g per pot (2×106 cfu / ml)] + Bacillus subtilis [10 g per pot (2×108 cfu / ml)] has recorded lowest wilt incidence (22.22 per cent), highest plant height (63.10 cm), fresh and dry weight of shoot (43.15 and 13.11 g) and root (12.88 and 3.85 g) respectively, less number of galls (51), egg masses (25.33) and root-knot index (4.00) were recorded compared to control treatment. Rhizosphere soil population of Ralstonia solanacearum also suppressed at final stage (0.30 × 106 cfu / g) when compared to 30 days after inoculation (55.20 × 106 cfu / g) due to suppression effects by bioagents.