[Two pleiotropic intervals of rice were assessed using NILs constructed by two methods]

Spikeletes per panicle (SPP) is one of the important yield components in rice (Oryza sativa L.). Appropriate heading date (HD) and plant height (PH) are prerequisites for desired yield. In this study, the near isogenic lines (NILs) of chromosome 7, which harbored QTLs controlling HD, PH and SPP were constructed based on the primary QTLs results of the recombinant inbred lines (RILs) derived from Zhenshan 97 and HR5. The near isogenic lines (RILs) of chromosome 8, which harbored QTLs of HD, PH, and SPP, were constructed using heterogeneous inbred family based on RILs. The genetic effects of two pleiotropic intervals were assessed accurately in these two NILs. The QTLs identified by the two near isogenic lines indicated that the three traits were controlled by the same QTL or tightly linked QTL. The QTLs controlling the three traits had the same direction on additive effects and dominant effects. And these traits showed bimodal or discontinuous distributions in respective NILs. These results imply that the same gene might control the three traits simultaneously (i.e., the gene pleiotropism). Along with this, the relationships between HD and PH and yield, the application of significantly positive correlation for the three traits in breeding program, and the advantage and disadvantage of the two constructing NILs methods were also discussed in this study.