Estimates of heterosis in winter/winter, winter/spring, and spring/spring crosses of barley (Hordeum vulgare L.)

Graduation date: 1980Previous work indicated a substantial heterotic expression for grain yield existed within winter/spring hybrids of barley, This research was a continuation for the comparison of the expression of heterosis within winter/spring hybrids to the heterotic effect produced among the winter and among the spring parents. The F₁ and F₂ progenies of one winter/winter, four winter/spring, and one spring/spring crosses involving two winter parents, 'Hudson', and 'Ager' and two spring parents, 'M21', and 'Karl' were studied. The experiment was a randomized-block design with two replications. Comparisons between the crosses were made by way of orthogonal contrasts. A very early spring planting date allowed sufficient cold exposure for vernalization of the winter habit material. Estimates of heterosis, heterobeltiosis, and inbreeding depression were obtained for the traits number of tillers per plant, 1000 kernel weight, number of kernels per spike, grain yield per plant, and plant height. Significant heterobeltiosis was detected for grain yield in only the F₁ winter/winter hybrid 'Hudson/Ager'. A significant negative heterosis for grain yield was expressed by the F₁ winter/spring hybrid 'Hudson/M21'. The winter/winter F₁ hybrid 'Hudson/Ager' was the only hybrid that expressed significant heterosis for plant height and tiller number, and was the only hybrid that did not express significant heterosis for kernel weight. Inbreeding depression in the F₂ occurred in most cases, but significantly in only three winter/spring crosses for the trait kernel weight. These results indicate that the winter/winter F₁ hybrid's expression of heterosis for grain yield was probably due to the contribution of the tillering component of grain yield. The failure of kernel weight in the winter/spring hybrids to have a heterotic effect on grain yield may have been prevented by yield component interaction. These results are not in agreement with data obtained from these hybrids in a previous year at another location, and suggest that the diversity between these winter and spring parents may not be sufficient to produce a heterotic expression across environments