Structure Analysis Of Wheat Powdery Mildew Population And Powdery Mildew Resistance Analysis Of Wheat Varieties(Lines)from Regional Trial In Shaanxi Province

Wheat powdery mildew is one of the most devastating diseases of wheat worldwide.Growing resistant cultivars is the most environmental friendly,economic and efficient approach to control this disease.However,the complexity of population structure of wheat powdery mildew,the rapid mutation and spread speed,and single resistant gene carried by resistant cultivars result in great challenges in conquering cultivar resistance.To provide effective information for predicting wheat powdery mildew epidemic and disease resistance breeding,the virulence structure and genetic structure of wheat powdery mildew population and resistance of 228 wheat varieties(lines)from regional trial in Shaanxi Province during 2016 were analyzed.To identify the virulence structure of wheat powder mildew population,powdery mildew samples from city of Weinan,Xian,Xianyang,Baoji,Hanzhong and Ankang during April and May were collected.160 isolates were obtained from these samples.32 wheat varieties(lines)with known Pm genes and software of PopGene32 and NTsys-2.10 e were used in the study of virulence structure of powdery mildew population.Results showed:(1)the virulence frequencies of V1,V2,V3 b,V3c,V3 e,V3f,V6,V7,V8,V19 and V1+2+19 were greater than 60%,which means their corresponding Pm genes are of little practical value.While the virulence frequencies of V4b?V24?V2+6?V2+Mld?V2+6+??V4b+Mli?V "Era" ?V "XBD" ?V21 were less than 20%,which indicates the corresponding resistant genes are valuable in wheat breeding.The collection of different resistant genes enhances the variety resistance and the durability of resistance;(2)Nei's gene diversity and Shannon's Information index were 0.2090~0.2895 and 0.3200~0.4502,respectively,which indicates the virulent diversity of powdery mildew population is not rich.Nm=6.0444 indicates the high level of gene flow.0.0030~0.0522 of virulent genetic distance and 0.9491~0.9971 of Nei's genetic identity show a high genetic identity;(3)data of geographic locations and cluster analysis show the relatively close relationship between virulent structure and locations of powdery mildew samples.To identify the genetic structure of wheat powdery mildew population,genetic diversity of isolates were analyzed using the method of ISSR-PCR.The results showed:(1)0.2636~0.3388 of Nei's gene diversity index indicates the high level of genetic diversity;(2)greater genetic distance and lower genetic identity of isolate compared with its virulent counterpart show a richer diversity,in terms of genetic aspect of pathogen population;(3)genetic variation within and among 6 groups accounted for 87.12% and 12.82%,respectively.So the variation within groups is the main resource of variation.3.4016 of Nm,which is less than 4,indicates the low level of gene flow;(4)DNA samples of 93 isolates were classified into 7 clusters,with the similarity coefficient 0.50.The isolates from the same location were classified into the same cluster.Thus,there are correlations between genetic distance and geographic locations.To evaluate the resistance to wheat powdery mildew of the known resistant genes and the wheat varieties(lines)from Shaanxi Province regional trial during 2015-2016 crop season,32 wheat varieties(lines)carried these known resistance genes and 228 varieties(lines)from province regional trial were tested in the disease nursery at seeding stage and adult stage,with the methods of artificial inoculation and natural infection,respectively.Samples of powdery mildew on wheat leaves were collected from different locations in Shaanxi Province.The results show that resistance genes of Pm4 a,Pm4b,Pm13,Pm17,Pm18,Pm19,Pm21,Pm24,Pm30,Pm2+6,Pm2+Mld,Pm2+6+?,Pm5+6,Pm”XBD” were immune or highlyTo resistant to wheat powdery mildew,and Pm3 a,Pm3b,Pm6,Pm4+8,Pm4b+Mli,Pm4+2+? showed weak resistance and the remainder resistance genes were susceptible.Among 228 province regional trial varieties(lines),14 varieties(lines)were resistant both at seeding stage and adult stage,and 33 varieties(lines)were resistant only at adult stage,accounting for 6.14% and14.47%,respectively.Most of these varieties(lines)were susceptible to wheat powdery mildew.