Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/8/2006
Publication Date: 1/22/2007
Citation: Robins, J.G., Luth, D., Campbell, T.A., Bauchan, G.R., He, C.N., Viands, D.R., Hansen, J.L., Brummer, E.C. 2007. Genetic mapping of biomass production in tetraploid alfalfa (medicago sativa l.). Crop Science. 47: 1-10 Interpretive Summary: Gains have not been made in alfalfa yield since the early 1980s. This is in contrast to the large yield gains achieved in other crop species, such as corn. Improved breeding strategies, such as hybrid varieties, will potentially increase alfalfa yields. However, we do not have a good understanding of the genetics controlling alfalfa yield. A better understanding of the underlying genetics could make the breeding of alfalfa for increased yield, and other traits, more efficient. In this study, n population of alfalfa plants was placed at three sites (Ames, IA; Nashua, IA; and Ithaca, NY) and evaluated for yield over three years. In addition, random polymorphic fragment length (RFLP) and simple sequence repeat (SSR) molecular markers were evaluated on the population to create a genetic linkage map. With the yield data from the field sites and the genetic linkage map, statistical analyses were used to identify the molecular markers on the genetic linkage map associated with alfalfa yield. These associations identify regions of the alfalfa genome that might be important for use in future selection efforts for the improvement of alfalfa yield.
Technical Abstract: Biomass production represents a fundamental biological process of both ecological and agricultural significance. Heterosis for biomass production occurs upon crossing particular genotypes. The genetic basis of biomass production, and of heterosis, is unknown. To address these issues we developed a full sib, F1, mapping population of autotetraploid alfalfa by crossing two genotypes of M. sativa subsp. falcata by M. sativa subsp. sativa that were known to produce heterosis. We developed genetic linkage maps of the genomes of both parents using RFLP and SSR molecular markers. We grew the population at three locations (Ames, IA; Nashua, IA; and Ithaca, NY) and collected biomass production data over a period of three years at Ames and Nashua and two years at New York. Transgressive segregants, many of which exhibited high levels of heterosis, were identified at each sampling period. Using single-marker analysis to identify QTL associated with biomass production and heterosis, we found QTL associated with these traits being contributed by both parents. These results suggest that both germplasm sources (M. sativa subsps. sativa and falcata) contain genomic regions that contribute to increased biomass production and that these are partially complementary, suggesting loci important for heterosis.