Changes in mean, variance, and covariation among agronomic traits in successive backcross generations of interspecific matings (Avena sativa L. × A. sterilis L.) of oats
F2-derived lines from BC0 through BC5 of eight Avena sativa × A. sterilis matings were evaluated for days to heading, plant height, biomass, grain yield, straw yield, harvest index, vegetative growth rate, and unit straw weight. The, A. sativa lines were used as the recurrent parents in all backcrosses. The evaluation experiment was conducted in a randomized-block design with two replicates and microplots each sown with 30 seeds. For summary purposes, the means, variances, and genotypic correlations from the four matings with the same recurrent parent were pooled within each level of backcrossing. Regression analyses were used to describe the rates of change for genotypic variances and correlations as number of backcrosses increased. In all matings, the trait means regressed toward the recurrent parents as backcrossing progressed. Harvest index was controlled by additive gene action; earliness was partially dominant and tallness was completely dominant; heterobeltiosis occurred for high vegetative growth rate; straw yield and biomass showed either heterobeltiosis or complete dominance; and high grain yield was partially dominant. Unit straw weight showed a positive heterobeltiosis. Log genotypic variances decreased significantly over backcrosses for days to heading, straw yield, and harvest index, whereas for plant height and unit straw weight, the reductions were not significant. Regressions of genotypic correlations were significant for only 12 of 56 trait associations, and changes that did occur were of little consequence.Key words: backcross, interspecific mating, oats.