Pyramiding Of Yield-related Genes And Their Genetic Effect Analysis In Rice

Increasing crop yield has always been a major predominant object in rice breeding techniques in China. In the past several decades, the yield level of rice has been significantly improved mainly as the result of genetic improvement, increasing harvest index by reducing plant height making use of the semidwarf gene sd-1, and utilization of heterosis between varieties. However, the yield of cultivars released in the past two decades has not been significantly improved. The breeding of super-high-yielding rice cultivars has been the focus of rice breeders.Japonica rice is an important type of Asian cultivated rice (Oryaz sativa L), which has been extensively disttributed in northern China, Japan and other countries or regions. In recent years, the yield of japonica rice has increased significantly. More and more rice breeders and geneticists have realized that the utilization of panicle erectness in japonica rice was the key factor in increasing japonica rice yield level. At present, over a half of japonica cultivited regions have been planted panicle erectness cultivars, and have an increasing tendency.Compared with the drooping panicle, the erect panicle type rice has higher yield potentialities, but most panicle erectness (PE) cultivars were derived from the cross of Balilla or Balilla-derived varieties with other parents. It has narrow genetic basis, poor heterogeneity, smaller grain, higher unfilled grain rate and poorer quality. So it is necessary to make genetic improvement for erect panicle type further.In this stdudy, we foucus on the genetic analysis of qPE9-1on the yield, grain quality through consctucting the near-isogenic lines for qPE9-1, wich confers the erect panicle trait. Addtionally, with the help of molecular markers, the favorite allele on GS3and Gn1a from indica varieties were pyramided with qPE9-1in the Wuyunjin8 background, and the evaluation of their genetic effects were performed. The main results were follows:(1) By molecular marker-assisted selection, the allele qPE9-1in Wuyunjing8was introgressed into Nongken57, which serves as recurrent parent. Thus a pair of near isogenic lines (NIL) with Nongken57genetic background was developed. The genetic model of erect panicle trait, and the agronomic traits of NIL-qPE9-1were analyzed.The results show that the erect panicle trait is contolled by a major QTL and erect panicle character is dominace to drooping panicle. The plant height of NIL-qPE9-1was dramatically decreased by～20%when compared to that of NIL-qpe-1. Similarity, the length of panicle, tiller number, interrnode Ⅰ,Ⅱ,Ⅲ and the length of up three leaves were decreased. As for the panicle characters, the number of secondary branches and the number of grains on secondary branches of NIL-qPE9-1did not altered significantly compared to those of NIL-qpe-1; while the number of primary branches and grains on primary branches of two NILs were different, and the values of NIL-qPE9-1smaller than those of NIL-qpe-1. The grain yield per plant of NIL-qPE9-1was only23g, while-34g for-NIL-qpe-1. The results also indicated that qPE9-1has pleiotropic nature. The quality characters of near-isogenic lines was analyzed, the result shows that AC, GC, CPV, PKV, HPV of NIL-qPE9-1were decreased when compared to that of NIL-qpe-1, indicating that the panicle type had an effect on quality characters(2) By molecular marker-assisted selection, the the allele Gnla from Habataki and the allele Gs3from Minghui63were introgressed into Wuyunjing8, which habors the gene qPE9-1, thus, the backcross population were obtained for the ananlysis of the genetic effects of Gnla and GS3.The agronomic traits analysis of Gnla backcross population shows that the gene Gn1a exhibites additive effect. The plant height was decreased, the length of panicle, the number of secondary branches, the number of grains on secondary branches and the grain number per panicle were increased significantly. However, the seed set rate and grain weight were decreased.The agronomic traits of GS3populations were analyzed; the result shows that the grain length, the grain length-width ratio increased, the grain width and the number of grains on primary branches decreased. And the the grain weight increased.