A Preliminary Study On The Distorted Segregation Of The Male Sterile Line Mian7-M In Brassica Napus L.

Segregation distortion is defined as abnormal segregation ratio of gene frequency or genotype frequency in some genetic loci that deviating from the Mendelian ratio.Segregation distortion often occurred in the process of reproduction, include the process of meiosis, fertilization and embryogenesis. Segregation distortion often caused by genetic factors which involve in the gamete selection and zygote selection and result in allele frequency changed in the progeny population. Therefore this phenomenon is often thought to be a potent evolutionary force.In the process of hybrid-breeding, a male sterile two-types line of brassica napus named Mian7-M was found, the rate of sterile plants from the its selfing progeny or sib mating progeny is deviating from the Mendelian ratio. In this research, we analysis genetic characteristics and make a preliminary explanation of the segregation distortion in Mian7-M. We used genetics and molecular biology experiment to determine the male sterility genes of Mian7-M as well as the genotype characteristics in its selfing progeny and sib mating progeny. Meanwhile, we did cytological experiments to detect the stage of the segregation distortion happened. The main conclusions were as follow:(1)Hybrid test showed that the segregation distortion in Mian7-M only happened in the male gamete transference. when Mian7-M or S45 was pollination with the pollens from Mian7-MB, the progeny often showed segregation distortion, however, when Mian7-M was pollination with the pollens from S45 B, the rate of progeny showed Mendelian ratio.(2)The male sterility genes of S45 and Mian7-M are genetic allelism. Differently, the male sterility of S45 is controlled by BnaMs1/Bnams1 loci, while Mian7-M is controlled by BnaMs2/Bnams2 loci.(3)Molecular markers were used to detect the genotype and gene frequency in the selfing progeny and sib mating progeny of Mian7-M and found the genotype of male sterility plant is Bnams1Bnams1Bnams2Bnams2, the genotype of male fertile is Bnams1Bnams1BnaMs2Bnams2, without the Bnams1Bnams1BnaMs2BnaMs2 genotype.Statistics found that Bnams2 gene frequency was significantly higher than that of BnaMs2.This phenomenon reflect that a segregation distorter loci linked with BnaMs2 that causedsignificant difference of transmission frequency of BnaMs2 and Bnams2 from parent to progeny.(4)The cytology experiments were done and found that the meiosis and male gamete activity were normal in Mian7-M, while the process of embryogenesis of several zygotes were abnormal. Combining with the analysis of the zygotes genotype from single silique in the segregation distortion population, we can conclude that the gamete selection and zygotic selection that lead the segregation distortion happened. Confirmed that the segregation distortion happened within the process of fertilization and embryogenesis.To sum up, the male sterility of Mian7-M is controlled by BnaMs2/Bnams2 loci. The gamete selection and zygotic selection in Mian7-M that caused the segregation distortion,which significant influence the transmission of BnaMs2 from parent to progeny and lead to the rate of sterile plants in progeny population was contrary to Mendelian ratio.