Abstract:
Bacterial wilt of tomato caused by pseudomonas solanacearum (E. F. Smith) is a serious disease causing considerable damage in crops grown in the acidic soils of Kerala. Development of resistant variety(s) could be a worthwhile attempt which would have considerable impact on tomato production in Kerala. Experiments were planned and carried out during 1981-82 at the Instructional Farm of College of Horticulture, Vellanikkara, Trichur, to incorporate two reported sources of resistance in F1 hybrids and then to find out inheritance of combined resistance to bacterial wilt.
Two distinct sources of resistance one derived from Louisiana pink possessing North Carolina type of gene system and the other from P1 127805A possessing Lycopersicon pimpinellifolium type of gene system were made use in the present study. Interspecific F1 hybrids were produced between the above two sources of resistance. The F1S were selfed to generate F2S. Parental lines, F1S, F2S were further grown to evaluate the inheritance of combined wilt resistance in a field which was known for disease susceptibility and inoculum potential.
The inheritance studies indicated a complementary and hypostatic type of digenic recessive gene system responsible for combined wilt resistance.
Interspecific F1 heterosis was estimated. Significant negative interspecific heterosis was observed for days to first flower, days to first fruit harvest, plant height, branches/plant, locules/fruit and fruit weight. Genetic distance (D2) was calculated to find out genetic similarity/dissimilarity between Lycopersicon pimpinellifolium (LE 218) and ten lines of Lycopersicon esculentum. The line LE 217 was observed farthest to Lycopersicon pimpinellifolium (D2 = 449.87). The line LE 212 was the closest to Lycopersicon pimpinellifolium (D2 = 159.96). The line LE 217 had a disease score of two indicating high field resistance. The tomato lines were further evaluated for incidence of nematodol root knots and observed that all the lines were susceptible to nematode.
The F2 lines possessing combined wilt resistance are being progressed for further study.
