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Abstract
Acid soils worldwide limit agricultural productivity due to the effect of aluminum (Al) toxicity on plant growth. Al toxicity inhibits root growth and development thus reducing biomass yield in important forage legumes including alfalfa. Medicago truncatula is a model legume species with an extensive genomics infrastructure that can facilitate discovery of Al tolerance mechanisms of value for economical important species. The objective of this research was to identify genomic regions relevant to acid and Al tolerance in M. truncatula using a recombinant inbred line (RIL) population. The mapping population was obtained from a cross between Mt Core 23 (acid and Al tolerant) and Mt Core 35 (acid and Al sensitive), followed by multiple generations of single seed descent. Genotyping of the F4:5 progenies was performed using the Illuminas Medicago Golden Gate array with 1,536 single nucleotide polymorphism (SNP) as well as, complementary genotyping of SNPs targeting genomic regions and Al tolerance candidate genes using high resolution melting (HRM) analyses. A whole plant assay was used to evaluate the phenotypic response of the individuals from the RIL population and the parents for root growth at pH 7, pH 4 and pH4 +Al 20 M. Genomic regionsassociated with Al tolerance were detected and the corresponding SNP markersidentified. The expression levels of target genes of contrasting genotypes were also evaluated. The practical value of the identified SNPs was evaluated based on their ability to predict the performance of additional RIL individuals when grown under acid and Al toxic conditions. Ultimately, strategies aimed to identify and understand genes and mechanisms of Al tolerance in Medicago are relevant and critically needed to deploy breeding strategies in economical important crops including alfalfa.