Genetic variability for cold tolerance in a maize (Zea mays L.) population

Research was conducted to improve our understanding of the genetic control of cold tolerance. Eighty-eight random S(,2) lines from the cycle 5 of the maize population BS13SCT were crossed in a North Carolina Design II. Reciprocal crosses also were made. Fullsib progeny were divided into 11 sets and grown in six early planted Corn Belt and Italian environments with three replications per set. Cold tolerance was evaluated using six traits: (1) percentage emergence at 200 and 400 growing degrees, (2) dry weight per plot and per plant, (3) rate of emergence on a day and growing degree basis, and (4) seedling vigor;Additive genetic variance was important for all cold tolerance components in all environments. Maternal genetic variance was present for the traits seedling vigor, and percentage emergence at 200 and 400 growing degrees in the Corn Belt environments and dominance genetic variance was present for seedling dry weight in all environments. Reciprocal genetic variance was not important for any trait measured in this population. Genotype x environment interaction subdivisions were consistently significant for all traits in each environment. Heritabilities were moderate for environments with significant genotypic differences and comparable to other studies, however, their standard errors were large. Correlations among seedling vigor, dry weight per plot, seedling dry weight, and percentage emergence at 200 and 400 growing degrees were positive, while those among rate of emergence on a day and a growing degree basis and the previous traits were negative. The Corn Belt and Italian environments were distinct sets of environments and different gene complexes might have been important in the two environment sets. The selection criteria utilized are dependent upon the type of environment encountered for evaluation