Genetic Analysis Of Stripe Rust Resistance Genes In Wheat Germplasm C273

Wheat stripe rust is one of the important diseases of wheat in the world and China.Reasonably utilizing wheat resistance genes and cultivating and planting resistant varieties are the most effective measures to reduce the harm of stripe rust.With the continuous emergence of new physiological races of stripe rust,many resistance genes have gradually lost their resistance.Exploring and applying new resistance genes to stripe rust is an urgent problem in production.C273 is a local wheat variety from Pakistan.Previous reports have shown that C273 has good resistance to the prevalent races of stripe rust in Pakistan for many years,but its response and resistance characteristics to the physiological races of stripe rust in China have not been reported.This study conducted phenotype identification and genetic analysis on C273 to explore its resistance gene loci to stripe rust.The main results are as follows:（1）C273 has a high level of resistance to stripe rust.Multiple different physiological races of stripe rust were used for seedling test.The susceptible control CB037S showed stable and highly susceptible behavior;C273 showed moderate to high resistance to single race CYR32,CYR34（collected from Gansu）,CYR34（v26-Lab）,and mixed races（collected from Tai’an in 2020）.In Tai’an,Shandong and Chengdu,Sichuan,mixed races were used for resistance identification during the adult stage.C273 showed high resistance to mixed spores collected in Tai’an in 2017 and 2020,as well as mixed spores collected in Chengdu in 2022.The above results indicate that C273 has effective resistance to the prevalent races of stripe rust in China and can be used as an excellent source of resistance to stripe rust.（2）It is speculated that the seedling resistance of C273 is controlled by a dominant gene Yr C273.F₁generation was created using susceptible material CB037S and high resistance stripe rust germplasm C273.Furthermore,F₂and F_2:3populations were created by self-crossing for genetic analysis of resistance genes.Using mixed races（collected in 2020）for seedling inoculation,both parent C273 and F₁generation showed resistance to disease.The F₂（C273/CB037S-B3）population showed significant segregation,and the number of disease-resistant and susceptible individual plants matched a 3:1 segregation ratio（123:35,χ²=0.683,p=0.49）,indicating that the seedling resistance of C273 to stripe rust is controlled by a dominant single gene,and it is temporarily named Yr C273.（3）Obtained molecular markers linked to Yr C273.Using BSR-Seq analysis of F₂（C273/CB037S-B3）population,the Yr C273 gene for resistance to stripe rust during seedling stage was mapped.BSR-Seq sequencing data shows that chromosome arms such as 7BL,5BL,4BS,and 2AS have SNP/In Del aggregation regions,with 7BL being the most significantly associated with phenotype.Furthermore,molecular markers were developed according to SNP sites on 7BL chromosome.The genotyping results showed that there was a significant correlation between molecular markers on 7BL and phenotypes,and codominance molecular markers C25,C45 were linked to Yr C273.（4）The relationship between Yr C273 and other known stripe rust resistance genes.The resistance performance and genotypes of linkage markers of different races indicate that C273does not carry Yr18 linked to leaf tip blight phenotype,and Yr46 from Pakistani wheat.And C273 also doesn’t carry seedling resistance genes Yr2,yr MY37,Yr041133,and Yr ZH84located on 7B.Now,it is speculated that Yr C273 may be a new wheat stripe rust resistance gene.