Fine Mapping Of S40, A Gene Responsible For Interspecific Hybrid Abortion In Rice (Oryza Sativa L.)

Rice is one of the most important food crops in our country. The stability and growth of rice yield are of great importance for our food security. However, the rice yield of our country is stagnant, and the narrow genetic resources are one of the main reasons. In order to further expand the rice genetic resources, transferring excellent genes from wild rice into cultivated rice is an effective method. Wild rice has some excellent traits, such as resistance to salinity, drought tolerance and resistance to pests and diseases. If these excellent genes could be transferred into cultivated rice, it would improve the yield and quality of cultivated rice. However, the sterility of F1derived from oryza sativa and wild rice puts obstacles in the way of taking advantages of these genes. The identification and cloning of new sterility genes, the analysis of their function and the definitude of the mechanism they have in regulating rice fertility are very necessary for the creation of new promising rice germplasm.In this study, we fine mapped a hybrid sterility gene S40and conducted a close cytological observation. Main results are listed as follows:1. The cytological observation of the hybrid abortive F1plant.At first, the pollen fertility of hybrid F1plant was half of the parental lines.Aniline blue staining revealed that many nomal pollen grains of the F1plant could adhere to the stigmas and were able to germinate, which were as same as the RD23. Excess pollination could not recover the impaired spikelet fertility, which means it was not the pollen sterility that caused the spikelet abortion.Laser confocal microscopy assay showed that half of the mature embryo was abnormal and empty embryo sacs without cell contents or incomplete embryo sacs were formed.Then we counted the number and ratio of abortive (degenarated and empty) embryo sacs and found that it was correlated to the fertility of spikelet.These datas showed that the low spikelet fertility was due to the partly abortive embryo sacs. Parafin section assay indicated that the abortion was caused by the disintegration of the functional megaspore, then the next development was blocked.2. Fine-mapping of the hybrid sterility gene S40.First, we screened the background of the near isogenic line, and found that there were two fragments substituted on the Chromosome1and Chromosome10respectively, the other parts were from parent RD23.The gene was primarily located between the molecular maker RM6289and hlyll using a NIL/RD23F2population, with a genetic distance of17.3cM on the Chromosomel. A large F23population containing5800plants were screened in2012and28recombinants were obtained. Progeny test was made in Hainan in2013.Further experiments and functional studies are ongoing.