RFLP facilitated analysis of tiller and leaf angles in rice (Oryza sativa L.)

Plant type is an important composite trait associated with the yield potential in rice and other cereal crops. Several characters associated with the plant type of modern rice cultivars including tiller angle, leaf and flag leaf angle, were investigated using a complete linkage map with 115 well distributed RFLP markers and progeny testing of 2418 F-2 derived F-4 lines from a cross between O. sativa ssp. japonica cv. 'Lemont' and spp. indica cv. 'Teqing'. One major gene (Ta) and 11 QTLs were largely responsible for the tremendous variation of the three plant type characters in the Lemont/Teqing F-2 population. The major gene, Ta, located between RZ228 and RG667 on chromosome 9, accounted for 47.5% of the phenotypic variation in tiller angle and had large pleiotropic effects on both leaf and flag leaf angles. This gene plus four QTLs accounted for 69.1% of the genotypic variation in tiller angle. Eight additional QTLs for leaf and flag leaf angles were also identified, which collectively explained 52.0 and 66.4% of the genotypic variation of these traits. Ta and three QTLs (QFla2, QFla5 and QFla7) apparently affected the related plant type characters differently, suggesting their possible differential expression in different developmental stages of rice plants or possibly clustering of different genes affecting these traits. Plant type, and consequently grain yield of rice, may be improved by deliberately manipulating these QTLs in a marker-assisted selection program.