Mapping and characterization of quantitative trait loci for mesocotyl elongation in rice (Oryza sativa L.
Mesocotyl elongation is an important trait for seedling emergence in direct seeding cultivation in rice. In this study, a backcross inbred line (BIL) population from a cross between Kasalath and Nipponbare was employed to map quantitative trait loci (QTLs) for mesocotyl elongation. A total of 5 QTLs for mesocotyl length were identified on chromosomes 1, 3, 7, 9, and 12 in 2 independent experiments. At all QTL, the Kasalath alleles contributed to an increase in mesocotyl length. Two QTLs (qMel 1 and qMel 3) on chromosomes 1 and 3 were consistently detected in both experiments. To fine map the QTLs, a cross was made between 2 chromosome segment substitution lines (CSSL 6 and CSSL 15) each harboring the Kasalath allele across the qMel 1 and qMel 3 regions, and an F2:3 population was developed. A two way ANOVA indicated that no epistatic interaction was detected between the 2 QTLs in the F2 population (P 0.31) Moreover, analysis of two F3 near isogenic lines (NILs) derived from the same cross, indicated that the 2 QTLs act additively in distinct or complementary pathways in controlling mesocotyl elongation. Substitution mapping indicated that the qMel 1 QTL was located between the 2 SSR markers RM5448 and RM5310, which are 3,799 kb apart, and that the qMel 3 QTL was located between the 2 SSR markers RM3513 and RM1238, which are 6,964 kb apart. To our knowledge, this is the first report to fine map QTLs for mesocotyl elongation and to analyze their interaction.
Rice