Combining ability and heterosis for forage yield among elite alfalfa core collection accessions with different fall dormancy responses
Understanding genetic parameters of populations that are being considered for inclusion into plant-breeding programs provides critical knowledge to enhance economic traits of interest. The objective of this study was to determine the genetic parameters influencing forage yield for nine populations selected from the USDA National Plant Germplasm System alfalfa (Medicago sativa L.) core collection that possessed high-yield potential and differing fall dormancy response. Forage dry matter yields of 36 diallel hybrids, their 9 parents, and 6 commercial checks were harvested three times in each of 2 yr from seeded plots near Las Cruces, NM. Variation among hybrids for forage yield was primarily attributed to general combining ability effects, which were 5.6 times greater than specific combining ability effects. More than 70% of the hybrids performed similarly to the best commercial check. Fourteen hybrids exhibited significant mid-parent heterosis (MPH), and seven hybrids exhibited significant high-parent heterosis (HPH). The frequency of hybrids showing significant MPH was twofold greater for hybrids generated between parents with different fall dormancy response as compared with hybrids generated from parents with similar fall dormancy response. Eight of the nine top-yielding hybrids were derived from populations that originated from Peru and Argentina. All hybrids with significant positive HPH involved a population from South America.