Quantitative trait loci affecting flag leaf development in rice (Oryza sativa L.)

One hundred and ninety-one recombinant inbred lines (RILs) (F-7) derived from a cross between Milyang 23 (M23) and Akihikari (AK) were grown in 1997 in Joetsu, Japan (temperate zone), and during the 2000-01 dry and wet seasons (four consecutive seasons) in Los Banos, Philippines (tropical zone) to detect quantitative trait loci (QTLs) for flag leaf length, width and angle (FLL, FLW and FLA) of rice (Oryza sativa L.). The detected QTLs suggested that flag leaf development was influenced by nine genomic regions categorized into three groups. In Group I, three regions (chromosomes 1, 4 and 6) increased both FLL and FLW. The QTL profiles showed that the effects of these three regions were powerful and stable across locations. Especially, the effect of the region on chromosome 4 (the nearest RFLP marker, XNpb235) accounted for 9-17% and 20-26% of the FLL and FLW variances, respectively. In Group II, four regions (chromosomes 2, 3, 10 and 11) affected FLL, whereas in Group III, two regions (chromosomes 8 and 12) affected FLW. The detection pattern of QTLs showed that three regions in Groups II and III (chromosomes 3, 10 and 12) were expressed by the growth conditions of Los Banos. No region with a clear effect on FLA was identified, although this trait was segregated largely in the RILs. By characterizing the nine regions in detail, this paper elaborates on the genetic factors and mechanisms controlling flag leaf development.