Molecular marker analysis of manganese toxicity tolerance in rice under greenhouse conditions

Two rice genotypes, an upland japonica rice Azucena and an indica rice IR1552, were found to differ in tolerance for Mn toxicity based the Mn toxicity symposium in the screening experiments in acid soil with higher available manganese level. Therefore, a recombinant inbred line (RIL) population in the F-9 generation consisting of 150 lines derived from a cross between the two parents was used in soil pots experiment under greenhouse conditions using an acid soil with a high available manganese level of 25 mg Kg(-1). Genotypic variation in tolerance for Mn toxicity was evaluated using Mn toxicity index (MTI) based on the degree of necrotic brown spots on the leaves and Mn concentration/content in shoots. Two hundred and seven markers covering 2419.5 cM on rice all 12 chromosomes were used by single marker loci and interval mapping. The results indicated that the two parents differed in MTI and Mn concentration and/or content in shoots, and these parameters were associated with Mn toxicity tolerance. The RILs showed a segregation for the above parameters. Molecular marker loci associated with variations in MIT values and Mn concentration/content in shoots were identified and eight QTLs associated with Mn toxicity tolerance were detected. Comparison of the marker genotype class means indicated that 6 of 8 tolerant alleles detected were contributed by the tolerant parent IR1552.