Responses to Aluminum in Ecotypes of Medicago Truncatula.

Aluminum (Al) makes up approximately 7% of earth’s crust. Most forms of Al are non-toxic; however, under acidic conditions, Al is solubilized into the soil solution where it rapidly inhibits root growth. To study Al tolerance in legumes, we assessed Al responses in eighty-two Medicago truncatula accessions collected from different geographic regions. Root growth measurement and root staining assays were used to define the sensitivity of each accession. Seedlings were grown in an agarose medium, containing three levels of Al and root length was measured at 24, 48 and 72 h after exposure to Al. Relative root growth (RRG) differed among genotypes. Aluminum accumulation in roots was also tested by hematoxylin staining. Sensitivity/tolerance to Al, as measured by RRG was correlated positively with the intensity of hematoxylin staining assays. Based on these results, we selected 3 sensitive lines and 3 tolerant lines for further genetic mapping analyses. The identification of Al tolerance could provide information to breed for improved crop production in legume species.