QUANTITATIVE INHERITANCE IN CROSSES AMONG FOUR TETRAPLOID WHEATS

Abstract

Four lines of Triticum durum, representing diverse levels of genetic relationship and geographic origin, were crossed to produce six segregating populations. Additive and dominance components of genetic variance were estimated for five metric characters in the F2and F4generations grown in separate years. Dominance variance predominated in two out of the six populations in F2, but was minimal in the F4generation. Additive genetic variance generally constituted the major source of genetic variance and was significantly greater than zero in all populations for every character investigated in F4. Populations based on crosses involving either of the two Ethiopian selections with either of the two North American varieties used as parents, in general showed larger amounts of genetic variance than the comparable intercross of the two North American varieties. Considerable genetic variance also existed in the populations derived from intercrossing the two Ethiopian wheats. The results of the investigation tend to support the hypothesized increase in genetic variance associated with genetic diversity, and the preponderance of additive genetic variance in naturally self-fertilizing species.