POLLEN VIABILITY AND FRUIT-SET OF TOMATO GENOTYPES UNDER OPTIMUM-TEMPERATURE AND HIGH-TEMPERATURE REGIMES

Heat-tolerant and -sensitive Lycopersicon esculentum Mill. and L.pimpi nellifolium (Jusl.) Mill. genotypes were grown in the greenhouse under optimum- (27/23C, day/night) and high-temperature (35/23C) stress reg imes, Heat tolerance levels in the genotypes were established by deter mining percent fruit set at high and optimum temperatures. Under optim um temperature, fruit set ranged from 41% to 84% and from 45% to 91% i n the heat-sensitive and heat-tolerant genotypes, respectively. Under high temperature, no fruit set in the most heat-sensitive genotypes. F ruit set in the heat-tolerant genotypes ranged from 45% to 65%. In vit ro germination and tube growth of pollen taken from genotypes grown un der optimum temperature conditions were determined before and after su bjecting the pollen to 45C for 1, 2, and 4 hours. The response of poll en to heat treatments was genotype dependent and not a general predict or of fruit set under high-temperature stress.