Population Genetic Diversity And Dispersal Of Puccinia Striiformis F.sp.tritici In Gansu And Qinghai Provinces

In China,wheat yellow rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most destructive diseases of wheat.Gansu and Qinghai provinces are the most important over-summering areas for wheat yellow rust in China.Thus,it is important that the analysis of population genetic diversity and the relationship of inoculum sources of Pst between two regions becomes important in the interregional epidemics and prediction of yellow rust.In this study,we compared the population genetic structure in a total of 2763 Pst isolates collected in 18 counties of Gansu and Qinghai provinces during in April 2017 to April 2019.And all Pst isolates were amplified using 16 pairs of simple sequence repeat(SSR)markers modified with fluorescent.In order to clarify exchange of inoculum source of Pst in spring epidemic time in Gansu and Qinghai provinces,the population genetic diversities,the potential spring epidemic migration and reproduction mode of Pst were investigated.The population dynamics of yellow rust pathogen in Gangu of Gansu province was also explored.At the same time,the population genetic relationship of Pst collected from late-maturing spring wheat,volunteer wheat seedlings and early autumn seedlings were analyzed.The results were as following:1.During the spring epidemic of wheat yellow rust in Gansu Province,10 Pst populations from different regions had high genotypic diversity(G=0.825),especially the Huixian and Qingshui populations in Tianshui,which had a genotype diversity as high as 1.A total of 373 unique multi locus genotypes(MLGs)were identified after clone correction cross the 452 Pst individuals.There were 6 MLGs shared in different regions,in which 2 MLGs(MLG-285 and MLG-288)were shared between Huixian and Lintao populations,and MLG-42 shared between Maiji and Gangu populations,MLG-266 shared between Zhuanglang and Linxia populations,MLG-320 shared between Linxia and Lintao populations,MLG-322 shared between Wenxian and Lintao populations.In spring epidemic season,the Pst source in Linxia in central Gansu might originate from Zhuanglang in eastern Gansu,the Pst sources in Lintao might originate from Huixian and Wenxian regions.The genotypic diversity(G)in Gangu populations ranged from 0.66 to 1.00 with an overall of 0.91 when all samples from the different populations were pooled.The 16 SSR markers produced a total of 110 polymorphic alleles.A total of 740 unique MLGs were identified.Among the MLGs,46 were detected 2-8 times in 14 populations.There were shared 5 MLGs in North and South mountains populations showed the Pst population migrated among the regions.The results suggest Pst can survive year-round in Gangu of Gansu Province.The Pst population migrated among the regions,and the migration pattern was not related to altitude.The over-summering populations in North and South mountains were genetically different from each other and the Pst populations collected from the Valley had no relationship with any of the populations collected in the spring or fall.Signs of sexual reproduction,indicated by non-significant r Bar D values,were found in the populations collected in both North and South mountain regions in spring,fall and over-summering(Pst survive in volunteer wheat),but not in the Valley populations.2.The Pst population in Qinghai Province also has a high genotypic diversity(G=0.869),but the populations in the same region have different genotype diversity in different seasons.The G value of 2018O-CB population(0.970)from Qinghai was the highest,and the 2018S-JZ population from Qinghia was the lowest(0.706).There were shared 3 MLGs(MLG-251,MLG-305 and MLG-292)in different populations.The Pst has frequent gene flow between Jianzha,Guide,Huzhu and Chengbei regions in different seasons.In spring,the Jianzha region is the origin of Pst in Qinghai.The inoculum source spreads from Jianzha to Guide,and can also spread to Huzhu and Chengbei in the late-maturing spring wheat region.In summer,the Pst multiplies in the late-maturing spring wheat in Huzhu and the volunteer wheat in Guide region to generate a large number of Pst.In autumn,the inoculum source of autumn wheat in Guide region was mainly from the spread of Pst over-summering on volunteer wheat in Guide and Chengbei,and the late-maturing spring wheat Pst inocula in Huzhu and Chengbei regions could also be directly transmitted to autumn wheat.3.A total of 1596 MLGs were identified cross the 1836 Pst individuals in Gansu and Qinghai populations.The shared 3 MLGs(MLG-655,MLG-1019 and MLG-1039)supplied molecular evidence for migration between Gansu and Qinghai populations.Genotypic frequencies indicated gene flow in autumn mostly from Qinghai to Gansu whereas,in spring,this was from Gansu to Qinghai.It was speculated that the inoculum source on late-maturing spring wheat could be directly transmitted to autumn wheat,not necessarily through volunteer wheat.In spring epidemic,the migration occurred frequently among the populations.The Pst source in Qinghai might originate from both Pingliang,Lingxia and Wenxian,but it was mainly from Pingliang and Lingxia.4.The linkage disequilibrium test revealed that sexual recombination phenomenon occurs in spring,autumn and over-summering(volunteer wheat)in the locations of Gangu,Maiji,Qingshui,Wen county,Lintao and Linxia county populations in Gansu province,and Xining Chengbei population in Qinghai province.The sexual reproduction might contribute to the richness of genetic diversity of Pst in Gansu and Qinghai.