Genetic Analysis of Yield and Yield-Attributing Traits for High Temperature Resistance in Tomato.

High temperatures can significantly reduce tomato (Solanum lycopersicumL) yield. A 5 × 5 diallel cross was used under high temperatures in a greenhouse to estimate combining ability and understand the genetic basis of tomato genotypes under heat stress. Additive gene action was predominant in governing most heat-tolerant morphological traits; yield was governed by nonadditive gene action. A cross involving high × high general combining ability (gca) or high × low gca had better specific combining ability (sca) effects. The genetic components and proportions studies showed heat tolerance was governed by nonadditive gene action and is a dominant trait. The parental variance (Vr) and parent–offspring covariance (Wr) relationship (Wr–Vr) indicated that heat tolerance traits were governed by overdominance. Significant correlation occurred between yield and yield-attributing traits. Heterosis was high for yield and most yield-attributing traits. Heterosis breeding involving crosses with high gca parents ‘CLN1621E × Nagcarlan’ and ‘BL1176 × Nagcarlan’ could be used to improve tomato for yield during heat stress. Selection for heat tolerance traits should be in early generations followed by selection for yield. [ABSTRACT FROM PUBLISHER]