No abstract

Seed size‐seedling vigor relationships were studied with birdsfoot trefoil (Lotus corniculatus L.), alfalfa (Medicago sativa L.), and sainfoin (Onobrychis viciaefolia Scop.). Differences in seed size were separated into those among plants and within plants. Seed weight distribution patterns were measured for each plant. An additional study measured the effect of varying number of seeds per raceme upon seed size of sainfoin.Correlations among clones of seed size with seedling vigor were significant in birdsfoot trefoil, were not significant in alfalfa, and approached a significant level in sainfoin. Differences in seed size within plants were highly correlated with seedling vigor in all legume species. The degree to which seed size can be affected by regulating seed number per raceme was shown for five sainfoin plants.Seed weight distribution patterns varied widely among plants within a species. The importance of these patterns in selecting for seedling vigor and in obtaining genetic equality in the contribution of plants to a composite variety is discussed.

Optimum temperatures for germination of sainfoin seed and for seedling growth were determined in conjunction with studies of the effect of the presence or absence of the seed pod. Optimum temperature range for germination of sainfoin was from l5 to 20 C. A higher range of optimum temperature, 20 to 30 C, was found for seedling growth. The presence of pods at all temperatures reduced speed of germination and speed of seedling elongation. Pods on the seed slowed water absorption by 4 to 5 hr. A water soluble inhibitor which slowed the speed of germination of shelled seed was detected. This inhibitor was readily removed from the pod by washing. Mechanical restriction of germination by the pod appeared to be a minor factor in the total effect of the pod on speed of germination. There was no difference in field emergence rates of sainfoin seedlings from shelled and unshelled seed.

Twelve hybrids between two‐ and six‐rowed barley varieties were evaluated for heterosis for two complex traits through the component interaction approach. On the average, very low levels of heterosis were found for the complex traits (grain yield per plant and total leaf blade area per plant). Data were presented on some of the possible causes of the failure of component niteraction to produce heteroic effects for the complex trait. The negative association of kernels per head and weight per kernel and the lack of additivity for kernels per head were determined as possible reasons for the failure of component interactions to occur and produce heterosis for grain yield. No apparent reasons were found for the failure of component interaction to occur for TLA. Reciprocal differences in the components among the parental varieties may not have been sufficiently large enough to promote component interactions for TLA.

Percent cross‐pollination in sainfoin (Onobrychis viciaefolia Scop.) was estimated under three planting arrangements by using flower color and growth characteristics as genetic markers. The amount of cross‐pollination was dependent upon the planting arrangement. A substantial amount of crossing occurred when one row of a maternal multicut line was seeded between two rows of a sinplecut pollen parent. More than 90% of progeny produced by three white‐flowered maternal clones surrounded by rows of pink‐flowered pollen parents resulted from crosspollination. Eight to 28% cross‐pollination occurred between white‐flowered maternal clones and pink‐flowered male clones in two clone crosses under isolation with honey bees as pollinators.