Discovery Of Powdery Mildew Resistance Genes And Development Of KASP Markers In Wheat

Wheat powdery mildew is an airborne fungal disease caused by Blumeria graminis f.sp.tritici,which poses a great threat to wheat production safety.The most economical and effective way to control powdery mildew is to cultivate powdery mildew resistant wheat varieties with resistance genes.As the pathogen itself will continuously change with the replacement of wheat varieties,the existing resistant varieties will lose their resistance gradually.It is a long-term task to explore new genes for powdery mildew resistance,develop molecular markers of resistance genes and apply them to marker assisted breeding for powdery mildew resistance.This research is mainly carried out from two aspects:first,based on the previous clones of Pm21,through analyzing its homologous genes in the sixth homologous group of wheat and sequence comparison,the SNP that can distinguish Pm21 and its homologous genes on the 6A chromosome is determined,and transformed into KASP marker,which can be further verified by using the segregated population and natural population,and the development can be rapid and high-throughput detection of diagnostic markers of Pm21 can accurately identify the presence or absence of Pm21 gene in both segregated populations and natural populations,and is widely used in molecular marker assisted selection of Pm21 gene.Second,we found a wheat line SN5057 with high resistance to powdery mildew in the previous study.In this study,we used SN5057 to cross with the susceptible variety Yangguang5 to construct a separate population,and used BSA to combine 50K SNP chip technology was used to detect the polymorphism between two mixed pools constructed with different phenotypes.Genetic analysis and gene mapping of powdery mildew resistance genes in SN5057 were carried out,and KASP markers closely linked with them were developed.The main results are as follows:1.Based on the sequence of the Pm21 gene and comparison analysis with the homologous sequence in wheat,a diagnostic marker KASP-Pm21-802＿6A derived from the Pm21 gene and capable of rapid and high-throughput detection of powdery mildew resistance gene Pm21 was developed.This marker can not only accurately distinguish wheat variety Yangmai18containing Pm21 gene and wheat variety Xumai32 without Pm21 gene,but also can accurately distinguish homozygous resistant,susceptible and heterozygous genotype families in the segregated population;the presence or absence of Pm21 gene can also be accurately detected in natural populations.Therefore,the marker can be widely used in marker assisted selection,and breeding of wheat varieties with resistance gene Pm21,which can effectively serve the breeding of wheat resistance to powdery mildew.2.The F₂ population and F_2:3 families constructed by resistant parent SN5057 and susceptible parent Yangguang5 were identified disease resistance at seedling stage by a single powdery mildew race E09.The results showed that SN5057 was immune,Yangguang5 was highly susceptible.The ratio of resistant and susceptible plants in F₂generation was 3:1 by chi-square test.In F_2:3 families,the ratio of resistant families:segregated families:susceptible families was 1:2:1,which indicated that the powdery mildew resistance of SN5057 was controlled by a pair of dominant genes,and was temporarily named Pm SN5057.3.Constructed a DNA resistance and susceptible pools using bulk segregate analysis（BSA）and tested the polymorphisms between resistance and susceptible pools using a 50K wheat chip,and found that there were 204 homozygous polymorphism SNPs in the resistance and susceptible pools.It is mainly enriched on chromosome 6A.By aligning with wheat reference genome sequences,it was found that these markers were mainly located in the 446-560 Mb region of chromosome 6A.Therefore,it is speculated that SN5057 may have powdery mildew resistance gene on chromosome 6A.These SNPs were further transformed into KASP markers for genotyping in F₂ population,and the genetic map of Pm SN5057 was constructed.The nearest two markers to the disease resistance gene Pm SN5057 were KASP-Pm478 and KASP-Pm638,respectively.The genetic distances between them and the disease resistant gene were0.1 c M and 0.5 c M respectively,which can be widely used in marker assisted selection of Pm SN5057.