Genetic Differentiation Analysis On The Wheat Backbone Parent Bima No.4 And Its Four Sib-lines

Bima No.4 which had the characteristics of excellent comprehensive properties and abundant genetic foundation, was one of the most excellent backbone parents in China. And it had produced sixty-eight derivatives. In order to reveal genetic foundation of how Bima No.4 could become backbone parents and explore the evolution law of backbone parents, which would offer us the theoretical basis for finding new backbone parents in future. We analyzed the genetic differention between Bima No.4 and its four sib-lines by employing three molecular markers, SSR, EST-SSR, and STS, to compare the characteristics of their genome structure. Main results were as follows:1. Comparing main agronomic traits among Bima No.4 and its four sib-lines, it was showed that Bima No.1 and Bima No.4 were all inherited high 1000-grain weight from Quality, and the 1000-grain weight of Bima No.4 was higher than Bima No.1, but their 1000-grain weight were both higher than other sib-lines. The five sib-lines variety were all inherited high grain number from Mazha mai.2. As a whole, genetic contribution rate of Mazha was higher than that of Quality in the five sib-lines. Bima No.1 and Bima No.2 inherited more genetic component from Mazha, the percent were 47.9% and 47.7% respectively. Bima No.4 inherited less genetic component from Mazha, the percent was 43.6%. Bima No.2 and Bima No.4 inherited more genetic component from Quality, the percent were 41.1%and 39.5%. Bima No.5 inherited less genetic component from Quality, the percent was 32.4%.3. The genetic similarity coefficient indicated that the genetic differentiation between Bima No.4 and its four sib-lines was high. Bima No.4 had the lowest genetic differentiation with Bima No.2 and the average genetic similarity coefficient was 0.823. And then were Bima No.1 and Bima No.5, the average genetic similarity coefficients were 0.799 and 0.786 respectively . Bima No.4 had the biggest genetic differentiation with Bima No.6 and the average genetic similarity coefficient was 0.779.4. The 188 special loci between Bima No.4 and its four sib-lines were found. There were three source for the specific loci, 35.1% of them derived from Mazha, 50.5% of them derived from Quality, 14.4% of them were allelic variation of Bima No.4. Partial specific loci were quite close and defense on chromosome, which formed specific regions of Bima No.4, such as Xmwg60-1A-Xwmc329,BARC101-2BL-Xwmc501,Xgwm570-6AL-Xpsp3152,Xmag794-7AL- Xmag4044. According to genes and QTL loci which were localized on wheat genomes, it was found that most specific loci / regions of Bima No.4 were genes and QTL loci associated with agronomic traits such as yield, disease resistance, adverce resistance and adaptability were located, which might be the genetic basis distinguished Bima No.4 from its four sib-lines and became the backbone parent.