Genetic Diversity Analysis Of Ms2 Improvement Population Assessed By Gliadin And The Selection Of Molecular Marker Linked To Ms2 Gene In Wheat

The genetic diversity of recurrent selection population constructed with Ms2 male-sterile lines and other materials with high yield and disease ressistance and different HMW-GS such as Glu-A12*, Glu-D1x5+y10, Glu-B1x14+B1y15 was evaluated with gliadin markers in wheat. The gliadin spectras of parents, C6, C7, and C8 population were identified with A-PAGE. The genetic variance was detected among parents and three populations. Useful genetic information was also provided for the construction, evaluation and improvement of Ms2 reccurrent selection population. In order to promote the selective efficience of excellent male-sterile lines, the molecular marker linked to Ms2 gene was detected among isogenic lines with Ms2 and Rht10 gene with SRAP technology. The results were as follows:1. The polymorphism decreased graudually with the increasing of generations. Some new loci could be created through the free recombination, while some loci were lost in recurrent selection.A total of 63 gliadin bands were identified in twelve parents and improvement population according to different mobility on the gel. 46 gliadin bands were included into 12 parents, and the number of gliadin bands was on average 23, with a range of 18 to 30. Compared with 12 parents, that number of bands of improvement population ranged from 15 to 32, with an average of 23. 24. Polymorphic bands and 11 unique bands were detected in C6, C7, and C8 recurrent population, while only 7 polymorphic bands and 4 unique bands were identified in 12 parents. The gliadin pattern was different in three recurrent selection cycles. The number of polymorphic band was 17 in C6, 10 in C7, and 8 in C8. As to unique band, the number of that was also deduced from C6 (5) to C7 (2), and none unique band was detected in C8. The polymorphism inωandγ-zone decreased more significantly than that in other two zones.2. The genetic distance of parents and improvement population was calculated. The maximum and minimum genetic distance of parents was 0.5349 and 0.0213, respectively. Compared with these of parents, the maximum and minimum genetic distance of parents was 0.6585 and 0.0385, respectively. The distributions of genetic distance were different in three gene populations. From C6 to C8, the average genetic distance was 0.2687, 0.2652 and 0.1987, respectively. Statistically significant differences were detected between C7 and C8 with the T value of 37.9718. All the above indicated that the genetic variance was deduced in the process of recurrent selection.3. The cophenetic correlation coefficient was 0.74, indicating that the result of clustering had a good fit to the genetic similarity matrix. Two clusters were formed at 0.72 point: groupⅠ(45 individuals, GS mean = 0.782) and groupⅡ(31 individuals, GS mean = 0.772), and the result of PCoA also showed that two clusters were formed, but there were still high variations between and with in two group. Similar to C6, with good cophenetic correlation coefficient 0.74, the 95 individuals in C7 could be divided into twomain groups at 0.75 point: groupⅠ(57 individuals, GS mean = 0.797) and groupⅡ(17 individuals, GS mean = 0.846), which was consistent with the result of PCoA. By comparison, the clustering result of C8 also had a good fit to the genetic similarity matrix with cophenetic correlation coefficient 0.75, but most individuals were in a group at 0.78 point. The result of PCoA also showed that most individuals distributed uniformly. All the above also indicated that the genetic diversity was deduced in the recurrent selection.4. A number of 1BL/1RS translocation lines were accounted in parents and improvement population. The percentage of 1BL/1RS translocation line decreased with the selection of excellent HMW-GS. Four parents, including D9401, Lumai14, Lumai15 and Xiaoyan6, were 1BL/1RS translocation lines. The number of 1BL/1RS translocation line was 6 in C6, 3 in C7, and 3 in C8.5. The molecular marker linked with Ms2 gene was detected among isogenic lines with Ms2 and Rht10 gene with 837 combinations of SRAP primers. No co-segregated molecular marker was found after validation, though differences were detected with 25 combinations. All the above indicated the possible special structure of Ms2 gene, and it was necessary to try other methods in the next work.In conclusion, our result indicated a severe reduction in genetic diversity with the process of recurrent selection, and it was necessary to introduce elite breeding materials into the consequent cycles, which could be complementary to the loss of genetic variance, and thereby maintain the genetic diversity in the breeding programs. Furthermore, in order to gradually promote the level of population improvement and maintain the genetic diversity, the genetic database constructed for each recurrent population could provide precise information for the identification of the introduced germplasm. Meanwhile, we need try new methods to select the co-segregated markers with Ms2 gene, which could be responsible for the improvement of selective efficience of elite male-sterile lines as well as the cloning of Ms2 gene.