Combining Ability and Genetic Variation Among Novel Orchardgrass Germplasm Sources.

Yield gains in orchardgrass (Dactylis glomerata L.), like most cool-season grasses, have lagged compared to other crop species. The development of synthetic varieties may capitalize on combining ability: mother genotypes are selected after progeny testing. The progenies are obtained from polycrosses and their performance is a measure of the general combining ability of the mother genotypes. An initial step to this breeding strategy is the identification of combining ability in germplasm sources of interest for breeding. This study evaluated nine orchardgrass germplasm sources utilizing a diallel crossing design to determine general and specific combining abilities among population hybrids. Three forage harvests were taken each year for three years from population hybrids, parental populations, and commercial checks. Differences (P < 0.05) were observed among the entries for dry matter yield within harvests and on a total yearly basis. Population hybrids were identified with comparable or higher yields than the check varieties. Significant general and specific combining ability effects for dry matter yield were observed. A breeding population, derived from collections from the Altai region of Russia, possessed high overall general combining ability. A germplasm population, collected from Xinjiang Province in China, possessed SCA when hybridized with the germplasm from Japan and with the variety Latar, although this Chinese germplasm possessed low GCA. Genetic similarity among parental populations was not correlated with SCA, but one parent population with high within population similarity exhibited particularly high GCA. These results highlight a considerable variation in combining ability with potential use in breeding.