Breeding Of The Recessive Genic Male Sterility Line And Its Maintainer With The Background Of 195-14A By Marker-assisted Selection In Rapeseed (Brassica Napus)

Utiliaztion of heterosis is a very effective way to improve crop varieties. Backcross breeding is a very effective method to improve individual trait of varieties. The technology of molecular maker-assisted selection provides a very effective tool for backcross breeding because it can offer precise and rapid selection of the targeted gene. Recessive genic male sterility (RGMS) which has benefits of stable and complete male sterility and wide restorers has become one of the important ways of heterosis utilization. With the discovery of a RGMS line (9012A) and the selection of its homologous temporary line, three-lines hybrid production system of RGMS was to come true. It can obtain a 100% male-sterile population and solve the problem of removing 50% fertile plants of maternal line during two-lines hybrid production and raise the efficiency and purity of hybrid production. The key point of the three-lines hybrid breeding is the selection of the homozygous two-type line and its homologous temporary line.In this research, the recipient parent is a temperature sensitive cytoplasmic male sterility line 195-14A (Ms3Ms3ms4ms4frf), and the donor parent is a recessive epistatic interactions nuclear sterility line 9012A (ms3ms3ms4ms4RfRf). The new type of homozygous RGMS line and its temporary maintainer with the background of 195-14A were selected through backcross breeding with molecular marker assisted breeding methods. The veracity and reliability of molecular markers were evaluated by the field genetic test of the sibling and testcrossing offsprings. The main results of research are as follows:1. Six plants with the similar genetic background of 195-14A were selected out from 44 sterile plants, which had the genotypes of ms3ms3ms4ms4RfRfor ms3ms3ms4ms4Rfrf, in the F2 population of 9012A and 195-14A after background selection with AFLP markers. The F2BC1 generation was obtained by backcrossing the ten selected sterile plants with the recurrent parent 195-14A.2. The SCAR maker WSC1 which linked with Rf was used for foreground selection in the F2BC1 population. Combing the results of both the foreground selection and the background selection with AFLP markers, eight plants with the genotypes of Ms3ms3ms4ms4Rfrf and the similar genetic background with 195-14A were selected to backcross with 195-14A, selfing, and testcross with 9012A and TAM, respectively. The F2BC2 and F2BC1F2 generations were obtained by backcross with 195-14A and selfing. The phenotype investigation results showed the fertility segregation in the testcrossing offspring was in accordance with 3:1 or 1:1 respectively. It was proved that the marker-aided foreground selection was accurate.3. Seven plants with genotypes of Ms3ms3ms4ms4Rfrf and the genetic background similar with 195-14A in the F2BC2 population of 470 plants were selected out after both the foreground selection with 6 markers lingked to MS3 or Rf and the background selection with SSR markers. The F2BC3 generation and F2BC2F2 generation were obtained by backcross the selected F2BC2 plants with 195-14A and selfing respectievly. At the same time,36 plants with the genotypes of Ms3ms3ms4ms4RfRf or ms3ms3ms4ms4RfRf and 9 plants with the genotype of ms3ms3ms4ms4rfrf in the F2BC1F2 population of 282 plants were selected out by foreground selection. In the flowering season, some fertile plants with the genotypes of Ms3ms3ms4ms4RfRf were sib-crossed with some sterile plants, and some sterile plants testcrossed with the maintainer plants. The phenotype investigation results showed the fertility segreqation in the sib-crossing offspring was in accordance with 1:1, and the testcrossing offspring was 100% sterile. It was proved that the marker-aided foreground selection was accurate.4.46 plants with the genotypes of Ms3ms3ms4ms4RfRf or ms3ms3ms4msrRfRf and 21 plants with the genotype of ms3ms3ms4ms4rfrf in the F2BC2F2 population of 282 plants were selected out by foreground selection. The selected fertile plants with the genotype of Ms3ms3ms4ms4RfRf and the sterile plants with the genotype of ms3ms3ms4ms4RfRf were sib-crossed for the multiplication of the homozygous two-type lines, and the fertile plants with the genotype of ms3ms3ms4ms4rfrf were selved for the multiplication of the temporary maintainer line.