Traditional Combining‐Ability and Gardner‐Eberhart Analyses of a Diallel for Cold Resistance in Winter Wheat1

Abstract

Six soft red winter wheat (Triticum aestivum L. era. Thell.) genotypes were crossed in a diallel system to estimate gene action and heterosis as expressed for cold resistance. Following cold hardening in the seedling stage, parental and F1 genotypes were exposed to 2, −7, and −10 C for 4 hours and allowed to recover for 10 days. Both the traditional partitioning of genotypes and that by Gardner and Eberhart were performed. The F1 hybrids exceeded the better parents by 26% for regrowth tissue weight and by 30% for crown weight after freezing, averaged over all temperatures. These two characters were significantly correlated. The major portion of the genetic variability was associated with specific combining ability or specific heterosis effects due to dominance or addltive‐by‐additive gene action.