| Wheat is one of the most important grain crops all over the world,and is also the third grain crop after corn and rice in China;it plays an important role in ensuring grain production and national security.Due to long-term artificial selection and cultivation,a large number of potentially beneficial genes have been eliminated at the same time of the selection of genes beneficial to human beings,resulting in the genetic basis of wheat gradually tends to be single,which brings severe challenges to the development of wheat industry.However,wheat relative species(genus)have a large number of beneficial genes,which is an important source for genetic improvement of cultivated wheat.This study analyzed the distant hybrid progenies of wheat-Agropyron cristatum in cytological,transcriptomic,and physiological traits.The chromosome composition of these progenies was determinated,and the candidate genes and physiological characters of powdery mildew resistance were identified,which laid the foundation for the discovery and utilization of resistant genes to powdery mildew in Agropyron cristatum.The main research results are as follows:1.Cytological genomic in situ hybridization(GISH)was used to identify two lines of wheatAgropyron cristatum distant hybrid.The results of GISH showed that WAT-2020-17-6 was a wheatAgropyron cristatum 6P chromosome translocation type(2n=42,T·W/6P).The W-2020-17-1 line was the wheat background parent(2n=42,AABBDD),without Agropyron cristatum chromosome composition.2.The resistance to powdery mildew was evaluated for two lines derived from the distant cross between wheat and Agropyron cristatum.The results showed that WAT-2020-17-6 was highly resistant to powdery mildew,with a disease grade of 0-1.W-2020-17-1 showed moderately susceptible to powdery mildew,with a disease grade of 5-6.The infection process of the two lines inoculated with powdery mildew at different times was observed.There was no significant difference between two lines infected by powdery mildew at 0-24 h.Powdery mildew on W-2020-17-1 grew rapidly and the number of mycelium increased significantly after 96 h.3.Transcriptome sequencing was performed of two wheat-Agropyron cristatum distant hybrids under the stress of powdery mildew,and 13387 differentially expressed genes were obtained.The numbers of differentially expressed genes in two lines at 0 h,6 h,12 h,24 h,36 h,48 h,72 h and 96 h stress were 2279(VPCl vs VPK1),985(VPC2 vs VPK2),1609(VPC3 vs VPK3),1629(VPC4 vs VPK4),1286(VPC5 vs VPK5),802(VPC6 vs VPK6),1404(VPC7 vs VPK7)and 3393(VPC8 vs VPK8),respectively.The number of differentially expressed genes in the two lines was the highest at 96 h under powdery mildew stress.Gene ontology(GO)enrichment showed that differentially expressed genes mainly involved in photosynthesis,chloroplast membrane,chlorophyll,photorespiration,thylakoid,etc.,which was concerned on photosynthesis.Kyoto encyclopedia of genes and genomes(KEGG)pathway enrichment analysis showed that differentially expressed genes were significantly enriched in photosynthesis,plant-pathogen interaction,carbon metabolism,phenylpropanoid biosynthesis,glutathione metabolism and other pathways.The co-expression network analysis confirmed that the six modules related to resistance to powdery mildew,they were Midnightblue,Blue,Brown,Lightcyan,Turquoise and Tan;and 12 core genes by the names of TraesCS1A02G225200,TraesCS6A02G281300,novel.8020,TraesCS6D02G008600,novel.10169,TraesCS1B02G274700,TraesCS5D02G450500,TraesCS7D02G526100,TraesCS5D02G265500,TraesCS5B02G426500,TraesCS5A02G332900,novel.7975.Meanwhile,qRT-PCR was used to verify the expression of differentially expressed genes in the materials.The results showed that the genes TraesCS1A02G225200,TraesCS5A02G332900 and novel.7975 had the highest expression levels in the two lines at 0 h after inoculation with powdery mildew.The expression levels of TraesCS6A02G281300,TraesCS5D02G265500 and TraesCS5B02G426500 were the highest in the two materials after 6 h inoculation with powdery mildew.The expression level of novel.8020 was the highest at 36 h and 6 h after inoculation with powdery mildew in WAT-2020-17-6 and W-2020-17-1,respectively.The gene TraesCS6D02G008600 had the highest expression levels in the two lines at 36 h after inoculation with powdery mildew.The expression level of TraesCS1B02G274700 was the highest at 48 h and 36 h after inoculation with powdery mildew in WAT-2020-17-6 and W-2020-17-1,respectively.The expression level of TraesCS5D02G450500 was the highest at 6 h and 24 h after inoculation with powdery mildew in WAT-2020-17-6 and W-2020-17-1,respectively.The expression levels of TraesCS7D02G526100 in WAT-2020-17-6 and W-2020-17-1 were the highest at 6 h and 72 h,respectively.4.In order to determine physiological traits,the samples from two lines were taken at 0 h,6 h,12 h,24 h,36 h,48 h,72 h and 96 h after powdery mildew stress.The contents of chlorophyll a,chlorophyll b and total chlorophyll in WAT-2020-17-6 were higher than those in W-2020-17-1 at 48 h,72 h and 96 h.Among the antioxidant enzyme activities except CAT activity of WAT-2020-17-6 was lower than W2020-17-1 at 96 h after inoculation,SOD and POD activity were higher than W-2020-17-1 at 96 h after inoculation.The fructose content of WAT-2020-17-6 was lower than that of W-2020-17-1 at all time points except for the inoculation,the contents of soluble sugar,and sucrose and soluble protein were higher than those of W-2020-17-1 at 96 h after inoculation.The MAD content of WAT-2020-17-6 was higher than that of W-2020-17-1 at 0 h,6 h,12 h and 24 h after inoculation.The Pro content of WAT2020-17-6 was higher than that of W-2020-17-1 except that at 24 h after inoculation lower.The PAL activity of WAT-2020-17-6 was higher than that of W-2020-17-1 at all times after inoculation.The PAL activity of WAT-2020-17-6 peaked at 6 h,and the PAL activity of W-2020-17-1 peaked at 12 h. |
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