"Assessment of eterosis and combining ability for quantitative traits in tomato (Solanum lycopersicum L.)

Abstract

Cultivated tomato is a relatively recent addition in world’s important crops. There exists enormous variability for quality and yield related traits among different genotypes of tomato species. Like other tomato growing countries, tomato cultivation in Pakistan is also facing yield stagnation due to narrow genetic base of the existing tomato varieties and the onset of different biotic and abiotic stresses. Tomato crop thrives well at a temperature ranging from 13 °C to 39 °C. Tomato plants are sensitive to chilling temperature (0-12 oC), therefore, its yield is affected by frost and low temperature. Hence, chilling stress is the major yield limiting factor for tomato cultivation in the plain areas of Pakistan. In order to develop high yielding frost/chilling tolerant tomato varieties/hybrids, there is need to exploit the existing variability for different yield related traits in tomato. The selected genotypes with frost tolerance and high yielding traits could be hybridized to converge these traits in desired genotypes. The present study was designed to undertake the genetic analysis of various quantitative traits of economic worth. A set of 101 diverse germplasm entries was subjected to natural chilling temperatures in the field. Among all the screened genotypes only 18 lines were identified as frost tolerant. The selected lines were crossed with three high yielding testers. The parents and the F1 hybrids were planted at two different locations. The data for various quantitative traits was recorded and subjected to biometrical analysis to evaluate general combing ability (GCA), specific combining ability (SCA) and heterosis, as a step towards the development of genetically improved indigenous hybrids/varieties in tomatoes. For the better understanding of behavior of different traits, correlation analysis and principal component analysis (PCA) of parental lines and F1 hybrids was also done.