Exploitation And Utilization Of Powdery Mildew Resistance Gene Pm2 And Its Alleles In Wheat

Wheat（Triticum aestivum L.）is one of the main grain crops and also a pillar that supports our food security.High yield and stable yield of wheat have important meaning to the steady development of Chinese economy.In production,powdery mildew,gibberella zeae,leaf rust and other diseases seriously harm wheat yield.Wheat powdery mildew is a fungal disease caused by Blumeria graminis f.sp.tritici（Bgt）.In severe cases,it can cause wheat yield reduction of more than 50%.The control measures of wheat powdery mildew mainly include chemical control,physical control and discovery of wheat genes resistant to powdery mildew.Among them,chemical control of environmental pollution is more serious,physical control is time-consuming and laborious,the most advantageous method is to explore the powdery mildew resistance gene,transfer it into wheat breeding wheat varieties resistant to powdery mildew.Wheat had good resistance to powdery mildew gene Pm2,and had broad spectrum resistance without obvious linkage.It is of great significance to clarify its distribution and utilization frequency in cultivated strains/varieties.At the same time,the diversity of resistance gene haplotype is important to enhance the resistance of wheat.Coarse goat grass is not only a secondary resource bank of wheat,but also a valuable resource bank of resistance genes.It is of great significance for wheat resistance to powdery mildew to find new genes or alleles of known genes.In this paper,the distribution of Pm2 and its alleles were analyzed in hexaploid wheat varieties/strains,and the wheat powdery mildew resistance gene Pm2 and its alleles were identified from the germplasm resources of coarse goat grass.The results are as follows:（1）Screening of Pm2 and its alleles in resistant varieties/lines:641 wheat varieties and breeding lines were screened using wheat powdery mildew strain E09,and the resistant materials among them were screened.Hybridization of resistant and susceptible materials produced F₂,F_2:3,and 33 F_2:3populations controlled by a single dominant gene were screened according to the separation ratio.DNA was extracted from pure resistance,pure sensitivity and heterozygous families in these populations,and the resistance genes carried by these materials were mapped to the Pm2 locus on chromosome 5DS of wheat using molecular markers Xcfd81 and Pm2b-map-3.Therefore,it is preliminarily speculated that the gene in the material is Pm2.RNA was extracted from the material.Molecular markers JS320/305 and JS314/315 were used to amplify Pm2 site DNA fragments in the target material.The sequences were tested and matched with the Pm2sequence Blast published on NCBI.A KASP marker YTU-KASP-Pm2 was developed based on the comparison of Pm2a sequence with the corresponding loci of Chinese spring,which can be used to identify Pm2 gene accurately and rapidly.（2）E09 was used to screen 71 crude goat grass materials and identify their broad-spectrum resistance.33 resistant materials were screened.The DNA of 71 resistant materials was extracted and PCR amplification was performed using known molecular markers Xcfd81 and Pm2b-map-3.The target fragment could be amplified from all 71materials.The homologous clones of Pm2 and its alleles from 18 resistant materials were randomly selected for testing.It was found that there was a haplotype with a deletion of 64bp in the corresponding sequence of Pm2 from C.chinensis.After translation,the deletion results in premature termination of translation and loss of function of Pm2 and its alleles.Therefore,a diploid molecular marker YTU-QS-1 was developed for coarse goat grass material.The Pm2 alleles were amplified by YTU-QS-1 from 33 samples.