2017 ASHS Annual Conference

High temperature is often a major limiting factor for tomato production in subtropical and tropical regions. Traditional breeding of heat-tolerant crops is mainly based on phenotypic analysis and selection of individual or lines with higher yield. Most abiotic stress tolerance traits are polygenic and inherited in a complex fashion. Studying correlation and the genetic control for heat-tolerance traits under high temperature stress facilitates heat tolerance selection. We determined the main gene effects (additive, dominant and epistasis) for heat-tolerance traits including pollen viability, flower number and fruit number per cluster, and fruit set by analyzing the mean and variances of the six genetic generations (P₁, P₂, F₁, F₂, BC₁ and BC₂) of two crosses ‘Freshmarket 9’ x ‘Black Sea Man’ and T215 VR x ‘Manyel’ in two locations in Texas. In the cross ‘Freshmarket 9’ x ‘Black Sea Man’, dominance effects were significant for all traits except pollen viability in Waller. In the cross T215 VR x ‘Manyel’, additive effects were found significant for all traits, while only pollen viability showed significant dominance effect in College Station. At Waller, only dominance effects were found significant for fruit number per cluster and fruit set in Waller. Narrow sense heritability estimates for pollen viability and flower number per cluster were low in both locations, and for fruit number per cluster and fruit set were low in College Station but moderate in Waller. The low narrow sense heritability estimates for most of the traits under high temperatures imply that single plant selection in the F₂ will not be effective, and that alternative approaches such as mass or recurrent selection should be considered in early generations.