DIALLEL ANALYSIS OF TOLERANCE TO ALUMINUM IN ALFALFA

Acid soils having high levels of aluminium (Al) can drastically reduce yields in alfalfa and the most economically viable solution to the pr oblem appears to be the development of Al-tolerant cultivars. To assis t with the choice of a breeding method, a six-parent alfalfa diallel ( crosses and reciprocals included but not parents) was evaluated in Al- toxic nutrient solution in terms of height (HT) and dry weight (DW). G eneral combining ability was significant for both traits and constitut ed the majority of the genetic variation. Specific combining ability w as significant only for HT and reciprocal effects were significant onl y for DW. Tolerance appeared to be at least partially dominant to sens itivity. Results indicate that a mass selection scheme, such as recurr ent phenotypic selection, may be effective in increasing levels of tol erance in at least some alfalfa populations and that minor grains may also be achieved through exploiting non-additive genetic variation.