Research Of The Yield Traits Of Wuyunjing 8 Improved By Gn1α

Rice is an important worldwide cereal crop and increasing crop yield has always been the predominant object in rice breeding in China. During the past half century, the yield level of rice has been twice dramatically improved as the result of using the semidwarf resources and the advantage of heterosis by producing hybrids. However, the yield of rice cultivars has not been significantly improved in the past two decades. In order to realize the third green revolution in the rice production, rice genetic breeders put forward different solutions. Combining utilization of the idea type and heterosis was put forward in our country. To increase yield per plant is still the main way to increase rice output, and panicle traits as the important index of high-yielding rice plant type are the keys to increase yield per plant. Grain number per panicle is the most important part of panicle traits, the improvement of it is very important to shape ideal plant type and improve the yield per plant.In this study, a japonica cultivar Wuyunjing 8 was used as the recurrent parent and another japonica line SL402 as a donor parent. SL402 is a chromosome segment substitution line derived from the cross of Sasanishiki/Habataki and the indica Gnla allele from Habataki is on the segment of substitution. We introgressed the indica Gn1a allele controling the grain number per panicle with additive effect into Wuyunjing 8 through multiple generation backcross combining marker-assisted selection to reduce the segment length. In the advanced backcross populations, we analyzed the genetic effect of indica Gn1a allele, its contribution to the yield and measured the rice quality traits and the other major agronomic traits of typical modified strains. Those lines whose yield was increased and other traits were not significantly changed were selected and their seeds were harvest for planting. The main results are generalized as following:1. By investigating yield-related traits of advanced backcross lines BC3F6 and BC3F7, we found the number of secondary branch, grains on secondary branch, total grains per panicle increased significantly. Compared to the recurrent parent, the grain number per panicle and yield per plant of BC3F6 were increased by 36.34% and 8.70%, respectively; and in BC3F7 increased by 26.74% and 6.03%, respectively. Two representative lines L1 and L2 selected according to the yield-related traits, we found the yield per plant of field plot increased 5.74% compared with the parent. These results showed that the Gn1a has significantly genetic effect on increasing rice yield. It should be mentioned that the seed setting rate and 100-grains weight significantly reduced, maybe due to the genetic hitchhiking and this still needs further study.2. The comparison of the milling quality, appearance quality, nutritional quality, cooking and eating quality between Wuyunjing 8 and the representative lines L1 and L2, showed no significant difference. Environmental changes and the different field managements have impacts on the quality traits, may leading to slightly different individual characteristics.3. Identified by simple sequence repeat and sequence tagged site marker, the positions of the introgressed fragments in advanced backcross lines BC3F6 and BC3F7 were around 22.6M and 5.5M on chromosome 1. However, the substitution fragment position of representative lines L1 and L2 is around 22.6M. As the two loci of Gn1, Gn1a and Gn1b, are too closed, a larger population needs to be built to select lines containing only indica allele Gnla fragment.