Studies on gene-action, combining ability and heterosis of some economically important characters in tomato (Lycopersicon esculantum) with particular reference to processing

Abstract

The possibility of breeding tomato genotypes with high soluble solids-an important trait for both fresh market and processing varieties-large fruit weight, heterosis, gene-action and combining ability of some physiological, biochemical and morphological components of yield and/or quality with particular reference to processing were studied. Although total soluble solids (TSS) and fruit weight were negatively correlated, simultaneous selection for both traits from F2 onwards in the crosses involving 249-2 (TSS 8.5%) and low solid parents (TSS 4%) helped in breaking the correlation. By F6 many genotypes with high solids of above 6% and fruit weight of above 60 g were obtained. Relatively lower coefficient of variation for TSS and fruit weight from F2 onwards than yield and fruit number suggest these traits to be governed by fewer genes than reported earlier. The dialed analysis revealed additive and dominant genetic effects to be mainly governing most of the traits except fruit number and lycopene content. High general combining ability effects had a close correspondence with high mean expression for most of the traits. Five F1 hybrids with semi-determinate habit were heterobeltiotic for yield per plant, highest heterosis being of the order of 47% in the cross P1 x P2. Crosses with the high solids parents 249-2(P8) were observed to be superior for nutritional quality. Heterosis was observed for ascorbic acid content, indicating dominant gene action for this trait. Specific leaf area (SLA) and specific leaf dry weight (SLDW) were positively correlated with each other as also fruit weight. Small leaf area was observed to be dominant over large leaf area. Genetic divergence between parents and heterosis were not associated. Specific combining ability was a more important factor in obtaining heterosis.