Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2002
Publication Date: N/A
Interpretive Summary: Alfalfa occupies the fourth largest acreage among U.S. crops and is a very important hay crop worldwide. Unfortunately, yield/acre of alfalfa has reached a plateau. Alfalfa breeders have sought to exploit "hybrid vigor" as a means of breaking the alfalfa yield barrier. Hybrid vigor is achieved by crossing parents that were selected for their ability to combine in a manner which produces vigorous progeny. This report demonstrates that the differences among parents based on a molecular assessment cannot be used to select parents which will produce hybrid vigor; however, information derived from the field performance of potential parents can be useful in parental selection. The information in this report should be of value to both public and private alfalfa scientists who are attempting to improve alfalfa productivity.
Technical Abstract: Heterosis for biomass yield has been shown to exist between Medicago sativa subsp. sativa and Medicago sativa subsp. falcata. The objective of this study was to gain a better understanding of what morphological and genetic factors were most highly correlated with total biomass yield heterosis. We calculated genetic distances among nine sativa and five falcata genotypes based on amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR) DNA markers. Genetic distance did not correlate with specific combining ability (SCA) or mid-parent heterosis. In contrast, a morphological distance matrix based on seventeen agronomic and forage quality traits was significantly correlated with heterosis; the agronomic traits of maturity, mid-season regrowth, and autumn regrowth showed strong association with heterosis.