Diallel Crosses Among Burley Varieties of Nicotiana tabacum L. in the F 1 and F 2 Generations 1

Abstract

Burley F 1 hybrids averaged 9.8% more yield than the parent varieties combined over 2 years. Heterosis was also expressed for increased total alkaloids, taller plants, more leaves, and larger leaves. Estimates of genetic variances indicated that additive genetic variance predomnated in the combined analysis. However, large genotype X year interactions existed for measures of heterosis and for estimates of genetic variances. These interactions were so large for yield that neither variance of general combining ability nor specific combining ability was significant in the combined experiments. Hybrids showing greatest heterosis and largest yield did not generally arise from the highest yielding parents per se . Variances arising from maternal and reciprocal effects were negligible.