Genetic cataloguing of tomato germplasm towards isolation of line(s) resistant to bacterial wilt

Abstract

Bacterial wilt caused by Pseudomonas solanacearum is the single disease causing the greatest damage in tomato grown in the acidic soils of Kerala. Isolation of a line(s) tolerant/resistant would be a worthwhile attempt which would have considerable Impact on tomato production in Kerala. An experiment was planned and carried out during 1980-‘81 in the College of Horticulture, Vellanikkara to isolate tolerant/resistant line to bacterial wilt.

Seventy eight lines collected from different sources where genetically catalogued as per the Reports of the Tomato Genetics Cooperative, 1980. Field screening indicated the tolerance of one line, LE 79 (CL -32d - 0.1-19 GS) received from AVRDC, Taiwan. This line had indeterminate growth habit, green shouldered and medium sized fruits and the seeds covered by yellow gel. The line was grown in the field continuously for six seasons to confirm the tolerance/resistance. The susceptibility ranged from zero per cent to 1.34 per cent in the adult plant stage. Breeding methods like pureline and mass selection were adopted to improve the fruit size and other characters of the resistant line. Genetic information like realised heritability were gathered for plant height, primary branches per plant, days to first fruit set, days to first fruit harvest, fruits per plant, marketable fruits per plant, locules per fruit, marketable fruit weight per plant and to tail fruit weight per plant. The tolerance/resistance was tested using soils from susceptible plots. Here again, LE 79 showed freedom from disease infection. The artificial inoculation proposed by Winstead and Kelman (1952) caused susceptibility in the resistant line. This may probably be due to high inoculum density which alter the disease resistance.