Resistance Identification, Genetic Analysis And SSR Molecular Markers Of New Wheat Cultivars With Stripe Rust Resistance

The wheat stripe rust, a wheat leaf disease caused by Puccinia striiformis West., is one of the most serious diseases of wheat production all over the world, and also a major control object and key disease of winter wheat in China. The domestic and international production practice and research indicate that breeding wheat with strip rust resistance is the most economical, effective, and ecologic method for controlling wheat stripe rust.The stripe rust resistance of currently popularized wheat cultivars in Sichuan province are mainly come from the Chuanmai42, Guinong lines and Nannong92R lines, wherein the Chuanmai42is a novel productive lines with strip rust resistance, a hybridization breeding from CIMMYT synthetic wheat and Chinese wheat by Yang Wuyun, from Crops institute, Sichuan academy of agricultural sciences. Chuanmai42also performs a highly resistance for all Puccinia striiformis popular in our country currently, and it is the major popularized wheat cultivars in wheat plating areas of Sichuan province and the middle and lower Yangtze River at present.However, the cases of Chuanmai42affected stripe rust were found in Sichuan province from2009to2011, and a novel Puccinia striiformis mutant has been gained from the affected Chuanmai42by Zhuang Guisheng etc. By identifying the resistance via novel mutant, they discover that the wheat cultivars from62different places in Sichuan barely have resistance for the novel mutant, and the majority of reserved cultivars from39different places in Sichuan have no resistance at all. The stripe rust resistance gene of wheat in Sichuan is simple, and the novel Puccinia striiformis mutant will potentially threaten the wheat in Sichuan even nationwide. Therefore, a novel resistant resource of wheat stripe rust is required urgently.This study identifies the resistance of nine novels autonomously breeding wheat cultivars in greenhouse and field in continuous two years respectively, using the mixed cultivars of novel Puccinia striiformis mutant gained from Chuanmai42and epidemic Puccinia striiformis. Then we screened out the disease-resistant parents which show a stable disease resistance in both two conditions and wheat cultivars infected with stripe rust such as Chuanmai28and Chuanyu12, building isolated population respectively, analyzing their hereditary capacity of stripe rust resistance genes and sifting the SSR molecular marker linked with resistance gene. The main research results are as follows:1. Identification for stripe rust resistance of novel wheat cultivarsAfter seeding in greenhouse and two consecutive years’ identifying in field, we find out the cultivars which show the stable resistance to novel stripe rust strains CM42-X and currently epidemic Puccinia striiformis are "CD011Jian33"、"CD011Jian46"、"CD011Jian56"、"CD3779" and "CD3788"; the cultivars which show the stable resistance to currently epidemic Puccinia striiformis but perform a level-4infection for novel Puccinia striiformis CM42-X are "CD0534-5" and "CD3787"; the cultivar which show the susceptibility to novel stripe rust strains CM42-X and currently epidemic puccinia striiformis is "CD0534-4"; and "CD011Jian41" shows the resistance to current epidemic strip rust and phenotypic separation to novel stripe rust strains CM42-X with27plants of level-3and14plants of level-0. Chuanmai28and Chuanyu12show susceptibility for both novel stripe rust strains CM42-X and currently epidemic Puccinia striiformis, compared with Chuanmai42which shows disease resistance for currently epidemic Puccinia striiformis and performs a level-4infection for the novel Puccinia striiformis CM42-X.2. Analysis for hereditary capacity of novel wheat cultivars with stripe rust resistanceThe F1generation of "CD011Jian33" and Chuanmai28shows immunity or nearly immunity for both novel Puccinia striiformis CM42-X and currently epidemic Puccinia striiformis. The anti-infection proportions of F2generation are374:141and186:57, corresponded to the proportion of3:1by chi-square test (χ2=1.554&0.309, P>0.05). The result indicates that the resistance for both novel Puccinia striiformis CM42-X and currently epidemic Puccinia striiformis of the novel wheat cultivars "CD011Jian33" is controlled by a pair of dominance stripe rust resistance genes, temporarily named YrJ33.The F1generation of "CD011Jian46" and Chuanmai28shows immunity or nearly immunity for both novel Puccinia striiformis CM42-X and currently epidemic Puccinia striiformis. The anti-infection proportions of F2generation are380:139and186:59, corresponded to the proportion of3:1by chi-square test (χ2=1.554&0.309, P>0.05). The result indicates that the resistance for both novel Puccinia striiformis CM42-X and currently epidemic Puccinia striiformis of the novel wheat cultivars "CD011Jian46" is controlled by a pair of dominance stripe rust resistance gene, temporarily named YrJ46.3. SSR molecular markers of stripe rust resistance gene YrJ33The study screens out the marker Xcfd21from519pairs of SSR primers which are evenly distributed in21chromosomes of wheat linked with resistance gene YrJ33carried by "CD011Jian33". The result demonstrates that335of the374resistance individual plants are able to amplify polymorphism fragment accordance to resistance parent and resistance pool,122of the141infected individual plants are able to amplify polymorphism fragment accordance to resistance parent and susceptible pool. The linkage distance between Xcfd21and YrJ33is11.26cM via Mapmaker3.0analysis. We can conjecture that YrJ33may be located on the1D or7D chromosome of wheat based on the location of the maker Xcfd21is on the1DS and7DL of wheat.In conclusion, this study has screened out the novel wheat cultivars with stable resistance for novel Puccinia striiformis CM42-X and currently epidemic Puccinia striiformis, and they are the "CD011Jian33","CD011Jian46","CD011Jian56","CD3779" and "CD3788". The genetic traits analysis of the "CD011Jian33" and "CD011Jian46" indicates that the resistance is controlled by a pair of dominant nuclear genes, respectively named as YrJ33and YrJ46. The study screens out the marker Xcfd21linked with YrJ33by SSR molecular marker. The study can provide theoretical basis for preventing massive erupting of novel Puccinia striiformis CM42-X and assistant breeding with molecular markers of wheat stripe rust resistance, and also lays a foundation for further positioning and utilizing stripe rust resistance genes YrJ33.