Identification and confirmation of aluminum tolerance QTL in diploid Medicago sativa subsp coerulea

The acid, aluminum (At) toxic soils found throughout the USA are a major limitation to the productivity of cultivated alfalfa (Medicago sativa subsp. sativa L.). One strategy to overcome this limitation is to develop At tolerant alfalfa cultivars. The objective of this study was to identify quantitative trait loci (QTL) controlling At tolerance in diploid M. sativa subsp. coerulea genotypes, to be used for introgression of the QTL into cultivated, tetraploid alfalfa. Restriction fragment length polymorphism (RFLP) markers were used in conjunction with a callus growth bioassay to identify Al tolerance QTL in an F-2 population, and confirm them in a backcross population. Single marker analysis was used to rind significant (P < 0.05) associations between RFLP markers and callus weight means. A soil-based study, conducted with selected diploid, backcross individuals, verified that QTL markers identified in tissue culture were also associated with Al tolerance in whole plants growing in soil. Two RFLP markers, UGAc471 and UGAc502, were associated with At tolerance in the F-2 and backcross callus assays, and the study in soil. These RFLP markers can be used to introgress these QTL into cultivated, tetraploid alfalfa.