Heritability Analysis for Heat Stress Tolerance in Tomato (Solanum lycopersicum L)

The growing evidence of global warming and, its potential impact on crop production has prompted several physiological and genetical analyses under high temperature conditions. Optimum growing temperatures for tomato (Solanum lycopersicum L.) is less than 32°C and 24°C during day and night, respectively. Tomato is grown in sub-tropical and tropical regions of the world, where day and night temperatures exceed the optimum temperatures during summer which exerts potential heat stress on tomato production. With looming global warming, the temperature levels may go up even further. Objective of the present study was to estimate the heritability of the flower and fruit setting ability of tomato populations under heat stress conditions so that its improvement for these traits can be planned. We developed the multiple tomato populations using parents from heat tolerant lines, and heat sensitive lines from NC State tomato breeding program as well as AVRDC sources. The F₂ and F_2:3 populations were grown at Piedmont Research Station, NC where summer growing temperatures are higher than optimum for tomato production. Heritability estimates of one of the populations (NC10418; 230 HS-1(99) x NC 1CS) by regression analysis of off-spring on parents method for number of flowers per cluster, number of fruit set per cluster and fruit set index were 72%, 49% and 60%, respectively. We will also present results from other populations. There was a positive correlation (r=0.50, p<0.05) between number of flowers and number of fruit set per cluster, which was in close agreement with the past findings. These findings may be useful to investigate the genetic control of heat stress tolerance in tomato and make crop improvement in future.