GENETIC DISSECTION OF THE SOURCE-SINK RELATIONSHIP AFFECTING FECUNDITY AND YIELD IN RICE (ORYZA-SATIVA L.)

The genetic basis underlying the relationship between the source leave s (the top two leaves) and the sink capacity in rice was investigated in a replicated trial of 2418 F-2 derived F-4 progeny from an inter-su bspecific cross between cv. Lemont (japonica) and cv. Teqing (indica) and a complete linkage map with 115 well distributed RFLP markers. Pat h analysis indicated that 50% of the phenotypic variation in the prima ry sink capacity-grain weight per panicle was attributable to variatio n of the flag leaf area. Thirteen QTL and 30 pairs of epistatic loci w ere identified, which influence the length, width and area of the sour ce leaves and the size of the primary sink (panicles) panicle length, floret density and floret number per panicle. Two QTL (QLl3b and QLw4) and 7 pairs of epistatic loci are largely responsible for the observe d relationship between the source leaves and the sink capacity. The ot hers appear to primarily influence the shape of the source leaves or p anicle length/branching, and contribute little to the observed source- sink relationship and partially explain the yield component compensati on. Our results suggest that important QTL affecting the source leaves can be manipulated through marker-assisted selection to increase sink capacity, which might result in improved yield potential in rice.