Identification And Mapping Of Powdery Mildew Resistance Gene In Wheat Based On 90k SNP Chips

Common wheat(Triticum aestivum L.)is one of the important food crops in China,and its production security and supply stability are closely related to the food security in our country.However,there are a variety of diseases that affect the normal growth of wheat throughout growth period.Powdery mildew,caused by Blumeria graminis f.sp.tritici Em.Marchal(Bgt),is one of the diseases seriously endangering the growth of wheat.The most direct and effective ways to control powdery mildew is discovering and using the new resistance genes persistently in wheat.Thinopyrum ponticum,a wild relative of wheat,belongs to the tertiary gene source of wheat,which are the excellent genes source of wheat resistance breeding with such desirable traits as large-spike and fertile florets,resisting drought,cold and disease,etc.CH1532,a new wheat germplasm line created through wide crosses and chromosome engineering technology derived from thinopyrum ponticum.Its pedigree is zhong8701//TAP8430/Jimai 26,among them,TAP8430 is an octoploid trititrigia derived from thinopyrum ponticum,zhong 8701 and Jimai 26 are common wheat.In this study,genetic analysis was used to diagnose the genetic mechanisms of powdery mildew resistance in CH1532.ISelect 90 K SNP chip and SSR markers were used to map the resistance gene.The main results obtained are as follows:1.In this experiment,the populations F1,BC1,F2 and F2:3 derived from Taichang29/CH1532 and their resistant/susceptible parents were used to inoculate with pathotypes E09 for testing the powdery mildew reaction in the artificial climate chamber.The results showed that CH1532 was immune to Bgt isolate E09,and taichang 29 was highly susceptible to E09,and the resistance performance of all F1 were the same as that of the resistant parent CH1532.The populations BC1,F2 and F2:3 family lines all are separate,segregation ratios respectively were 1:1,3:1 and 1:2:1.So inferred that the powdery mildew resistance in CH1532 was controlled by one pair of dominant nuclear genes,which was temporarily designated as Pm CH1532.2.ISelect 90 K SNP chip was used to scan the disease resistance and susceptible pools constructed by Bulked Segregation Analysis.89 polymorphic SNP markers obtained were matched the flanking sequences with Blast N.The results indicated most polymorphic SNP markers account for 69(77.5%)were located on the 2nd homologous group chromosomes,of which 44 SNPs are on the 2D chromosome,the ratio is 49.4%.Mapping of chromosomes according to software Map Inspect showed that the distribution of SNP markers on the 2D chromosome is concentrated between635.6-650.3Mb regions.Those showed that Pm CH1532 may be located on the long arm terminal of 2D chromosome.3.Development of SSR markers between 2DL chromosomes635.6-650.3Mb for screening polymorphisms using published Chinese spring genome sequences.The 71 polymorphic markers were screened to detect a small population in the populations F2 derived from Taichang29/CH1532.Finally,six markers are closely linked to Pm CH1532,they were 2DL101,2DL115,2DL147,2DL167,2DL181,2DL198.4.In order todetermine further the chromosome location of PmCH1532,PCR amplification was performed on 374 individual plants of the F2 population using six markers.Then the position order of six markers was determined by calculating the linkage distance between the selected molecular marker and the disease resistance gene using Mapmaker Exp 3.0and Kosambi,and the linking relationship of six markers was2DL101-2DL115-2DL147-Pm CH1532-2DL167-2DL181-2DL198,of which2DL147 and 2DL167 located on both sides of Pm CH1532 with the linkage distance of 1.3c M and 2.7c M.5.PmCH1532 was located on chromosome 2DL by i Select 90 K SNP chip and SSR markers.Furthermore,Pm CH1532 compared with the physical map of Pm43 may be a new gene on the chromosome 2DL.