High temperature limit crop productivity as a consequence of global warming and climate change. In particular, high temperature interferes with sexual reproduction and thus fruit and seed formation in crops. In the present study, phenotypic evaluation of a tomato population, including 21 tomato genotypes, was carried out under high-temperature stress (35 degrees C). Several reproductive and yield-related traits, including the number of inflorescences, number of flowers per inflorescence, pollen viability, fruit set, number of fruits per plant, and number of fruits per inflorescence, were investigated. Significant positive correlations between pollen viability and fruit set were observed (r = 0.83). Based on the obtained findings, the fruit set, pollen viability, number of fruits per plant, and number of fruits per inflorescence were recognized as markers for heat tolerance screening of tomato genotypes. These traits effectively separate tolerant and sensitive genotypes, which can be used in breeding program. At the same time, the number of inflorescences and the number of flowers per inflorescence did not separate between tolerant and sensitive genotypes. In conclusion, heat stress, through influencing pollen viability and fertilization, imposes its effects on reproductive organ development in tomato genotypes.
