Regulating Effects Against Wheat Stripe Rust By The Genetic Diversity Of Wheat

Wheat stripe rust, caused by Puccinia striiformis.f.sp.tritici, is a worldwide fungal disease. It has brought serious damage to wheat and caused heavy yield loss in China. Due to the virulence variation of stripe rust and the planting of single species, wheat cultivar resistance is constantly losing. The utilization of genetic diversity to prevent wheat stripe rust receives increasing attention. To study the effects of different resistance genes in mixed groups on controlling wheat stripe rust, five cultivars of near-isogenic lines(Avocet S*6/Yr1, Avocet S*6/Yr6, Avocet S*6/Yr9, Avocet S*6/Yr24, Avocet S*6/Yr10)were chosen, each contained a resistance gene. The results were as follows:Mixed planting could reduce the occurrence of wheat stripe rust to a certain extent. At grain filling stage, proportion of the hybrid combinations whose actual diseased leaf rate was less than the theoretical value was 84.61%, with the relative control effect of 2.84%~39.23%. The hybrid combinations whose actual disease index was less than the theoretical value accounted for 53.84%, with the relative control effect of 17.87%~79.66%. Two cultivars mixture did not reduce the disease obviously and three or more cultivars mixture could mostly reduce disease significantly. Resistance genes in the mixed wheat could screen the physiological races of stripe rust, which might be related to the control efficiency. This could explain the phenomenon that the more resistance genes, the higher probability of disease mitigation. For rich genes could suppress the frequency of occurrence of dominant races.The hybrid combinations whose actual AUDPC was less than the theoretical value account for 53.84%, with the relative control effect of 16.96%~76.42% among the 2 species and 3 species of combinations, both positive and negative prevention effect existed. The combinations in which disease reduced mostly contained Avocet S*6/ Yr6 and Avocet S*6/ Yr10, while the combination of disease aggravating mostly contained Avocet S*6/Yr9 and Avocet S*6/Yr24. It seemed that, control effect did not simply depend on the number of resistance genes, gene type was also very important. There existed interaction among the resistant genes.Analysis showed that there were 12 mixed treatments whose 1000 grain weight increased, accounting for 92.31%, There were 10 combinations whose yield increases, accounting for 76.92%, indicating that mixed sowing could reduce yield loss.Analysis of the content of crude protein showed that combinations whose protein content improved account for 84.61%. Wheat hybrids could improve the protein content of wheat, and improve the quality of wheat in a certain extent.76 strains were collected from 3 treatments- Avocet S*6/Yr6、Avocet S*6/Yr10 and Avocet S*6/Yr(9+10). Through the identification of physiological races and AFLP analysis, we concluded that, genetic diversity was not identical in different unicast; compared with unicast, corresponding mixed sowing owned higher genetic diversity.