| Wheat stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major disease that can cause tremendous wheat production losses worldwide, especially in the cooler and wetter environments. Since the appearance of PST race CYR32and CYR33which are the most widely virulent and predominant pathotypes in China, a lot of wheat cultivars have become susceptible, resulting in the epidemic of stripe rust. Frequent changes in the pathogen population and the homology of stripe rust resistance background in commercial wheat cultivars are the main reasons of the epidemic. Therefore, using resistant cultivars is the most economical and safty method to reduce damage caused by this disease.Alien resistant gene transfer is a valuable means of increasing the amount of resistance diversity. The Thinopyrum species, Th. intermedium (Host)(2n=6x=42, JJSS) and Th. ponticum (Podp.)(2n=10x=70,JJJJSJS) had many excellent resistance gene for wheat disease, it is a valuable source of wheat resistance breeding. At present, more and more stripe rust resistance varieties derived from the two Thinopyrum species have been cultivated and used for wheat breeding. Recently, several new Thinopyrum-derived multi-resistance lines have been developed, and they are highly resistant to stripe rust. In this study, our aims were to determine the inheritance, chromosome location and linkage to molecular markers of these new lines. The main results are as follows:1. CH223is a Th. intermedium-derived wheat introgression line and resistant to stripe rust. To investigate the inheritance of stripe rust resistance introgressed from Th. intermedium, CH223was crossed to susceptible cultivars Taichung29and SY95-71to yield segregating populations. The F2, F3and BC1were tested for segregation of stripe rust resistance. Genetic analysis showed that resistance of CH223was controlled by a single dominant gene. An F2segregating population from CH223/Taichung29was further used for microsatellite screening and gene mapping. The resistance gene was linked to five co-dominant genomic SSR markers, Xgwm540, Xbarc1096, Xwmc310, Xgpw7272and Xwmc47, their most likely order was Xgwm540-Xbarc1096-YrCH223-Xwmc310-Xgpw7272-Xwmc47at21.9,8.0,7.2,12.5and11.3cM, respectively. Through the Chinese Spring nullisomic-tetrasomic and ditelosomic lines detection, the polymorphic markers and the resistance gene were assigned to chromosome4BL. As no stripe rust resistance gene was previously assigned to chromosome4BL, this new resistance gene was designated Yr50. Yr50, together with the identified closely linked markers, could be useful in marker-assisted selection for pyramiding stripe rust resistance genes.2. CH7102, the resistance to stripe rust was introgressed into common wheat (Triticum aestivum L.) from Thinopyrum ponticum, using a resistant partial amphiploid as a bridging parent in crosses with susceptible wheat lines. The evaluation of resistance reactions in this study demonstrated that the wheat line CH7102has exhibited a high level of resistance to Chinese Pst races CYR32and CYR33, the most widely virulent and predominant pathotypes in China. The resistance responses of CH7102to the races tested was similar to those of its donor parent Xiaoyan7430as well as the wild parent, whereas all the wheat parents involved were susceptible, indicating that the resistance conferred by CH7102was possibly derived from T. ponticum. The F1,F2, F3and BC1populations from a cross of CH7102with susceptible line were tested for segregation of stripe rust resistance. Genetic analysis all showed that resistance of CH7102was controlled by a single dominant gene. Through microsatellite screening five co-dominant genomic SSR markers were found linking to resistance gene, Xbarcl24, Xgwm636, Xgpw2204, Xgwm95and Xgwm296. Their most likely order was Xbarc124-Xgwm636-YrCH7102-Xgpw2204-Xgwm95-Xgwm296at5.0cM,8.6cM,8.4cM,2.7cM and14.4cM, respectively. Through the nullisomic-tetrasomic and ditelosomic lines detection, the polymorphic markers and the resistance gene were assigned to chromosome2AS.3.CH7115is another stripe rust resistance gene which was also introgressed from Thinopyrum ponticum. The resistance responses of CH7115to the races tested was similar to those of its donor parent Xiaoyan7430as well as the wild parent, which indicated the resistance of CH7115was derived from Thinopyrum ponticum. The F1, F2, F3and BC1populations from a cross of CH7115with susceptible line were tested for segregation of stripe rust resistance. Genetic analysis all showed that resistance of CH7115was controlled by only one dominant gene.Through microsatellite screening five co-dominant genomic SSR markers were found linking to resistance gene, Xgdm33, Xgwmll, Xcfd65, Xgwm18and Xbarc137. Their most likely order was Xgdm33-YrCH7115-Xgwm11-Xcfd65-Xgwml8-Xbarcl37at10.5cM,7.1cM,0.4cM,2.7cM and1.2cM, respectively. Through the nullisomic-tetrasomic and ditelosomic lines detection, the polymorphic markers and the resistance gene were assigned to chromosome IBS.4. TAI8335was a new partial amphiploid derived from Thinopyrum intermedium. CH7359was a homogeneous BC2F4-derived wheat lines using TAI8335as its donor parent. Through races test, CH7359showed similar phenotype to its donor parent and the wild parent, which indicated the resistance of Line CH7359was derived from Thinopyrum-intermedium. The F1, F2, F3and BC1populations from a cross of CH7359with susceptible line were tested for segregation of stripe rust resistance. Genetic analysis all showed that resistance of CH7359was controlled by only one dominant gene. After microsatellite screening three co-dominant genomic SSR markers was found linking to resistance gene. Using Mapmaker3.0software to map their linkage, we got their most likely order was Xgwm273-YrCH7359-Xgwm626-Xbarc24at8.6cM,5.9cM and3.2cM, respectively. Finally the polymorphic markers and the resistance gene were assigned to chromosome6BL.5. CH7203is another stripe rust resistance gene which was also introgressed from Thinopyrum Intermedium, using the resistant partial amphiploid TAI8335as a bridging parent crossed with susceptible wheat lines MianYang11. The resistance response of CH7203to the tested races was similar to those of its donor parent as well as the wild parent, which indicated the resistance of CH7203derived from Thinopyrum Intermedium. Genetic analysis of the F1, F2, F3and BC1populations from the cross of CH7203with susceptible line Mian Yang11showed that resistance of CH7203was controlled by only one dominant gene. Microsatellite screening results showed two co-dominant genomic SSR markers were linked to resistance gene, Xbarc170and Xwmcl61, their most likely order was YrCH7203-Xbarc170-Xwmc161at4.1cM,6.3cM, respectively. Through nullisomic-tetrasomic and ditelosomic lines detection, the polymorphic markers were assigned to chromosome4AL. But the two linking SSR makers were located the same side to resistance gene, the target gene was only assigned to chromosome4A. We need to find more tight linking markers to locate this new resistance gene exactly.In conclusion, through conventional hybrid analysis, we found stripe rust resistances of five wheat-Thinopyrum germplasm lines (CH223, CH7102, CH7115, CH7359, CH7203) were all controlled by a single dominant gene and the resistance was derived from Th. intermedium or Th. poticum. Resistance genes carried by the five lines were respectively assigned to4BL2AS, IBS,6BL and4A, using SSR molecular marker technique to analyze F2derivations. Both the resource and chromosome of these genes are different from other known stripe rust genes. Among them, a new resistance gene carried by CH223was formally designated Yr50. Identification and analysis of these new stripe rust resistance lines will be beneficial for map-based gene cloning and gene function characterization. Cytological analyses using GISH also detected no chromosomal segments from alien species, so the resistance of these new lines can be stably inherited. It will be available for wheat molecular marker-assisted resistance breeding and increasing the diversity of wheat resistance resource. |
PDF Full Text Request