Combining ability studies in tomato (lycopersicon esculentum mill)

Abstract

An experiment in tomato (Lycopersicon esculentum Mill.) was carried out at the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 1993-94, with the objective of estimating the combining ability of parents and gene action, involved in the inheritance of different yield attributes. The study was conducted in a line x tester model, using three bacterial wilt resistant varieties as lines and five popular varieties as testers. The three bacterial wilt resistant varieties (lines) were Arka Abha, Arka Alok and Sakthi. The five popular varieties (testers) were LE 312, LE 370, LE 373, RFH-1 and PKM-1. These eight parental varieties and 15 hybrids were planted in the field in RBD, with three replications. Observations recorded were plant height, number of branches/plant, growth habit, spread of the plant, period of harvest, individual fruit weight, number of fruits/plant, fruit yield/plant, number of leaves/plant, pericarp thickness, locules/fruit, size of fruit and pest and disease incidence. Analysis of variance revealed highly significant differences among the genotypes for all the characters. Gca alone was significant for number of branches/ plant while sca alone was significant for spread of the plant and pericarp thickness. Both gca and sca were significant for the remaining characters such as plant height, period of harvest, individual fruit weight, fruits/ plant, fruit yield/plant, leaves/plant, locules/fruit and size of fruit. The additive to dominance variance ratio indicated a preponderance for non additive gene action in the above characters. Combining ability analysis showed that all the three lines viz., Arka Abha, Arka Alok and Sakthi were good general combiners with respect to fruit yield and other yield attributes whereas the testers were good general combiners, for the different vegetative characters such as plant height, branches and leaves/plant. Among the 15 hybrids combinations, significant sca and heterosis were observed in the hybrids such as Arka Abha x LE 370, Arka Alok x PKM-1, Arka Alok x LE 312, Arka Abha x RFH-1 and Sakthi x RHF-1. Among these hybrids, Arka Abha x LE 370 showed significance for fruit yield, individual fruit weight, size of fruit, plant height, leaves/plant, branches/plant and also showed resistance to mosaic, leaf cur1 and fruit borer. This hybrid exhibited indeterminate growth habit. The hybrid Arka Alok x PKM-1 showed significance for fruits/plant, fruit yield/plant, plant height and leaves/plant. The combinations Arka Alok x LE 312 and Arka Alok x RFH-1 showed high sca and heterosis for individual fruit weight, fruit size and pericarp thickness, and also high heterosis for fruit yield/plant. Among these, Arka Aloka 312 showed indeterminated growth and Arka Alok x RFH-1 showed semi determinate growth habit. Sakthi x RFH-1 exhibited high sca for fruit yield/plant and heterosis for fruit number and individual fruit weight. This hybrid also showed resistance to leaf curl and mosaic. This hybrid showed determinate growth habit. Therefore these hybrids can be utilized for further crop improvement programme.