Fine mapping of the quantitative trait locus qFLL9 controlling flag leaf length in rice

The morphological traits of leaves, such as size and shape, are major determinants of plant architecture and strongly affect high yield performance. To understand the molecular mechanism governing flag leaf length, we analyzed quantitative trait loci (QTLs) affecting flag leaf length by employing 176 F-2 individuals derived from a cross between two japonica rice cultivars: Shennong265 (SN265) and Lijiangxintuanheigu (LTH). We identified qFLL3, qFLL6 and qFLL9 from this F-2 population. Flag leaf length was increased by SN265 alleles at qFLL3 and qFLL6, but by LTH allele at qFLL9. In order to eliminate the influence of qFLL3 and qFLL6, one single residual heterozygous plant for qFLL9 region, RH-qFLL9, was selected based on the genotypes of 114 simple sequence repeat (SSR) markers and used as the parent of a segregating population. Using this segregating population of 889 plants, this region was narrowed down to an interval between RM24423 and RM24434. According to the rice annotation project database, there are 17 predicted genes in the 198-kb target region.