GENETIC ANALYSIS FOR THE DETERMINATION OF HETEROSIS AND COMBINING ABILITY OF TOMATO FRUIT MORPHOLOGICAL TRAITS UNDER FROST STRESS.

Tomato production in Pakistan is facing stagnation due to different biotic and abiotic stresses. Tomato crop thrives well at temperatures ranging from 13 to 30°C. Tomato plants are sensitive to chilling temperature (0-12°C), 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 present study was designed to undertake the genetic analysis of various quantitative traits of economic worth. 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 (Faisalabad and Sialkot). The data for various fruit morphology traits were recorded and subjected to biometrical analysis to evaluate variability in parents and off springs. The yield performance of hybrids was evaluated at two different locations as a step towards the development of genetically improved indigenous hybrids/varieties in tomatoes. Maximum heterosis (78.11%) for marketable fruit yield per plant was calculated in F1 hybrid resulting from a cross involving 017856 and Roma. Likewise, maximum heterosis for fruit length, width and weight was recorded for F1 hybrids of BSX-717-1-1 × Roma (20.67%), Rutgar Sala × Nagina (50.80%) and CLN-2418 A × Roma (44.90%), respectively. Hence, suggesting the use of these parental genotypes for the development of frost tolerant and high yielding tomato varieties. [ABSTRACT FROM AUTHOR]