Tóm tắt
A partial diallel cross with 32 parental lines of alfalfa, Medicago sativa L., was evaluated to determine genetic variability and heterosis expressed for forage yield when pest‐resistant, low‐yielding parents were crossed with noninbred, vigorous germplasm. The parental lines included eight half‐sib family seed lines from two commercial cultivars, ‘Apalachee’ and ‘Arc,’ and from two pest‐resistant experimental populations, MSA and MSB. Progenies from the intercross of each of the parental lines were also included in the experiment. Significant mean squares for cultivars from which the parental lines were derived and for lines in cultivars were observed for the intercrosses of the parental lines and for general combining ability. In both cases, the mean square for cultivars was more than 20 times larger than the mean square for lines in cultivars. Significant specific combining ability was not detected. Interactions between genetic effects and years generally were not significant. Crosses had significantly greater yield than the mean of the parental line intercrosses for each of the cultivar combinations. Generally, crosses with lines from MSA or MSB as one of the parents yielded significantly less than crosses between lines from Apalachee and Arc, and crosses between lines from MSA and MSB yielded significantly less than crosses from any other cultivar combination. The intercrosses of parental lines from MSA had greater average yield than those from MSB, but parental lines from MSA had lower combining ability than those from MSB.
