Evaluation of a set of non-segragating and segragating populations of tomato for field resistance to bacterial wilt
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Date
1985
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Department of Olericulture, College of Horticulture, Vellanikkara
Abstract
Bacterial wilt caused by Pseudomonas solanacearum E.F. Smith is the single limiting factor for tomato cultivation in the warm humid tropical soils of Kerala. The susceptibility of reportedly resistant varieties elsewhere necessitates the need for continuous evaluation of tomato lines for wilt resistance. An experiment was planned and carried out during 1983-’85 at the College of Horticulture, Vellanikkara to identify new sources of resistance to bacterial wilt.
The susceptible check Pusa Ruby showed 100% susceptibility in all the trials. The F2 hybrids of Saturn and LE 79 were found resistant, out of the four non-segregating (Saturn, LE 79, Pusa Ruby and Pusa Ruby x LE 79 F1) and two segregating populations (Pusa Ruby x LE 79 F2, Saturn x LE 79 F2) evaluated. In a repeated trial F3s were also evaluated along with the F2s and non-segregating populations (Saturn and FE 79). Resistance was observed in Saturn x LE 79 F3 (percentage wilt, 10.7) and Saturn x LE 79 F2 (percentage wilt, 18.23). Pusa Ruby x LE 79 F2 s and F3s were susceptible to moderately susceptible. Among the non-segregating populations, LE 79 showed moderate resistance, while Saturn was moderately susceptible to susceptible in both the trials. Information on days to fruit set, days to harvest, fruit yield/plant and average fruit weight were also gathered. A higher average fruit weight (44.63g) was observed in the resistant Saturn x LE 79 F3s.
Evaluation of 15 reportedly resistant lines of tomato confirmed resistance in LE 79 LFG and LE 217. The line LE 79 LFG was also medium fruited (40.1g) and high yielding. Concentric cracking and irregular cracking were observed higher than radial cracking in all the lines evaluated. Fruit set ranging from 50 to 63% was observed in all the lines at higher night temperatures (230C average).
Genetics of fruit shoulder colour revealed that white colour was recessive to green and governed by a single gene.
Evaluation techniques like root dipping in bacterial culture and planting, stem inoculation in leaf axil and alternate row planting were compared with spot-planting for efficiency. Spot-planting was found easier and effective. The chances for escape are negligible in this method of evaluation.
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171065