| Wheat is an important crop in China,but with the changing environment,various pests and diseases as well as abiotic stresses are increasingly threatening,wheat production status and food safety are facing serious challenges.Fusarium head blight(FHB)is a kind of fungal disease that causes serious damage to wheat,the lack of germplasm resistant to FHB is the main problem of wheat resistance to FHB.Thinopyrum elongatum is an important wild relative of wheat,and it was found that its chromosomes carry resistance genes to FHB,which can be used for genetic improvement of wheat resistance to FHB.Although the introduction of exogenous chromosomes can improve wheat resistance to FHB,it will also bring about a chain of undesirable gene accumulation,which is of little significance for application in breeding.Therefore,small fragment translocation lines with more stable genetics and excellent agronomic traits is of more practical importance for wheat breeding in FHB resistance.In this study,we aimed to identify new germplasm with stable agronomic traits and excellent resistance to FHB from the wheat-Thinopyrum elongatum(2x)7EL chromosome fragment library through rigorous multi-generation resistance identification to FHB and molecular marker identification.At the same time,combined with transcriptome analysis to explore potential resistance genes and reciprocal genes,analyze the molecular mechanism of wheat resistance to FHB,and provide theoretical basis and germplasm resources for wheat resistance to FHB.The specific results of the study are as follows:1.we obtained a small fragment translocation line with stable agronomic traits and good resistance to FHB from the wheat-Thinopyrum elongatum(2x)7EL fragment variant library,and named it as YNM158.We used it to cross with susceptible material AN8455 and cultivated variety YM23.The results of identification of resistance to FHB and agronomic traits for two consecutive years showed that the resistance to FHB of the progeny was improved significantly compared with the parents,and the agronomic traits did not show a significant decline.After that,we crossed YNM158 with more than ten main wheat cultivars in the middle and lower reaches of the Yangtze River,and the FI generation showed excellent results of FHB resistance and was significantly better than the common wheat parents,which proved the potential application of the small fragment translocation line YNM158 in breeding for wheat resistance to FHB.2.Using common wheat China Spring and Thinopyrum elongatum(2x)as reference genomes,we analyzed the transcriptome data of YNM158 at different time points after inoculation,and combined with the qRT-PCR results,we found three genes of Thinopyrum elongatum that were significantly up-regulated after infection.Tel7E01G020600 encoded Glutathione S-transferase(GST),and its expression was significantly up-regulated at all infection time points.Further analysis revealed that this gene was a homologous of TpGST,which was tentatively named TeGST.and there were 10 sites of differences in nucleotide sequence and 7 differences in amino acid sequence between them.The TaJAZ-Fg gene encoded jasmonic acid structural domain(JAZ)protein,which interacts with the TeGST protein,was obtained by yeast two-hybrid assay screening.And qRT-PCR experiments showed that the expression of TaJAZ-Fg gene was significantly induced by FHB.Therefore,we predict that JAZ protein plays a potential role in the resistance to FHB of YNM158.Tel7E01G946300 encodes a blue cupric binding protein BCBP2,and the expression of this gene showed an overall upward trend and reached the highest level at 72 h after infection.In addition,Tel7E01G1980900 encodes a monosaccharide sensitive protein MSSP2,whose expression was significantly induced in the early stage of infection and was the highest at 2 h of infection,and then began to show a downward trend.However,the effect of Tel7E01G946300 and Tel7E01G1980900 on the resistance of YNM158 to FHB needs further study.3.In order to study the disease resistance mechanism mediated by exogenous chromosome fragments in YNM158,in this study,transcriptomic sequencing was performed on YNM 158 and YM158 infected by Fusarium asiaticum at different times.We took 8 h after infection as the time node,8 h before was the initial colonization stage and 8 h after was the initial colonization stage,and finally screened 4060 and 9808 differentially expressed genes at the initial colonization stage and infection stage.KEGG analysis of the differentially expressed genes showed that there are seven specific pathways at the initial colonization stage.Phosphatidylinositol signaling system and Glycerolipid metabolism are the most significant.And there are 21 specific pathways in the infection stage,of which Glutathione metabolism is the most significant.At the same time,there are 13 pathways enriched in both infection and initial colonization stages,among which Biosynthesis of secondary metabolites and Metabolic pathways are the most significant.WGCNA analysis of differential genes revealed that 847 genes were closely related to YNM158.After in-depth analysis of the differential genes which obtained from different stages and WGCNA analysis,we finally screened 6 genes which express significantly higher in YNM158 than in YM158.Further analysis revealed that these six genes were involved in endoplasmic reticulum protein synthesis and processing,plant pathogen interaction,and metabolic pathways.The endoplasmic reticulum protein synthesis and processing was the specific activation pathway at the initial colonization stage of YNM 158,the plant-pathogen interaction was the specific activation pathway at the infection stage of YNM158,and the metabolic pathway was activated at both stages of YNM158.Therefore,the introduction of 7EL chromosome fragment not only brought new resistance genes,but affected the disease resistance pathway of wheat in YNM158 at different stages of infection,thus improving FHB resistance of YNM 158.These results provide theoretical basis for further study of resistance mechanism of YNM158,and it is important for improving wheat FHB resistance by using YNM158. |
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