Influence Of Crown Rot On Rhizosphere Soil Properties And Root Development And Defense Mechanism In Wheat(Triticum Aestivum L.)

Crown rot is a serious disease that mainly harms the stem base and spikes of wheat.It generally occurs in world's wheat production region,affecting wheat grain yield and quality.Due to the lack of disease-resistant cultivars,chemicals are mainly used in production to prevent the epidemic of the disease,which is inefficient and not environmentally friendly.The promotion of disease-resistant cultivars is the most effective and environmentally friendly way to prevent the epidemic of diseases.Therefore,screening resistant germplasm and studying the pathogenicity of main pathogens of wheat crown rot and the resistance mechanism of wheat to pathogens will be beneficial to the breeding of resistant cultivars and the establishment of new methods for disease control.In this study,Fusarium pseudograminearum and Bipolaris sorokiniana,which were widely distributed and highly pathogenic,were used as pathogens to identify the resistance of 46 wheat cultivars(lines),185 recombinant inbred lines(RILs),which was constructed by hybridization between a disease-resistant(PI610750)and a disease-susceptible(UC1110)cultivar,and the effects of pathogens on wheat roots,rhizosphere soil,grain yield and quality.After inoculating pathogens at seedling stage,the differentially expressed proteins at the stem base of susceptible and resistant wheat cultivars were detected,and the main metabolic pathway of wheat in response to crown rot was identified.The main results are as follows:1.Through the indoor seedling experiment,F.pseudograminearum and B.sorokiniana were inoculated separately to identify the resistant germplasm.Luomai 18,Wenmai 19,Zhoumai 26,Yu nong 416,UP-114,UP-93,UP-29,UP-78,UP-95,UP-28 and UP-91 showed disease-resistance at seedling stage,and 38 cultivars(lines)showed moderate disease-resistance,including Yunong 202,PI610750 and synthetic wheat.In the response to F.pseudograminearum at seedling stage,UP-114,UP-93,UP-29,UP-78,UP-95,UP-28 and UP-91 showed disease-resistance,while 24 cultivars(lines)showed moderate disease-resistance,including Yunong 202,PI610750 and synthetic wheat.UC1110 showed high sensitivity to both pathogens.The results of variance analysis showed that the resistance responses of different lines of RILs population to the two pathogens at seedling stage were significantly different(P < 0.0001),and there was a significant positive correlation between the two pathogens in resistance phenotype.The number of crossing,total root length and number of branches of resistant and moderately resistant lines were higher than those of susceptible and highly susceptible lines.The results showed that the excellent resistant germplasm resources resistant to F.pseudograminearum and B.sorokiniana could be selected by RILs population resistance isolation of UP.2.A field pot experiment was conducted to clarify the effects of two pathogens of wheat crown rot on rhizosphere soil characteristics and grain quality.After infection with F.pseudograminearum,the frequency of disease rating of wheat was mainly distributed in grade 3 and grade 4.Compared with control,sucrase activity in rhizosphere soil decreased by 4.8% and 42.2% in response to F.pseudograminearum and B.sorokiniana,respectively.Grain protein content increased by 6.8% and 13.6%,while amylopectin decreased by 6.4% and 6.7%,respectively,and total starch content decreased by 5.4% and 5.8%,respectively.In response to B.sorokiniana stress,the content of ammonium nitrogen and alkali-hydrolyzable nitrogen in rhizosphere soil increased by 64.1% and 83.3% respectively,while the content of nitrate nitrogen decreased by 15.7%.The number of grains per spike of clum ear and grain yield increased by 17.9% and 17.5%,respectively.In response to F.pseudograminearum,the total nitrogen content increased by 9.7%,and the number of sterile spikelets in the clum ear increased by 77.8%,then the number of spikes and grain yield decreased by 18.2%and 33.2%,respectively.The results showed that the damage of F.pseudograminearum was serious.3.The results of quantitative proteomic analysis with tandem mass spectrometry(TMT)tags showed that 3 dpi,the average root diameter and MDA content of diseaseresistance cultivar PI610750 decreased,while the average number of root tips increased,and the root vigor of the two cultivars increased significantly,indicating that there were differences in root morphology,physiology and biochemistry between the two cultivars.Through GO enrichment and KEGG analysis,a total of 366 DEPs were identified in the two comparison groups UC1110₃dpi/UC1110₀dpi and PI610750₃dpi/PI610750₀dpi.Phenylpropanoid biosynthesis,secondary metabolites biosynthesis,linolenic acid metabolites,glutathione metabolism,plant hormone signal transduction,MAPK signal transduction and photosynthesis contributed to the defense mechanism in wheat.Protein-protein interaction network analysis showed that the DEPs interacted in both sugar metabolism and photosynthesis pathway.Sixteen genes were validated by real-time quantitative polymerase chain reaction and were found to be consistent with proteomic data.The main conclusions of this study are as follows:(1)F.pseudograminearum is the dominant pathogens of crown rot,and the RILs population resistance isolation of UP is an excellent germplasm resource for breeding resistance to F.pseudograminearum and B.sorokiniana.(2)Wheat was seriously damaged by F.pseudograminearum,and there were differences in soil characteristics and grain quality in response to the two pathogens.(3)There are differences in defense mechanisms between UC1110 and PI610750 against F.pseudograminearum.The defense of PI610750 against F.pseudograminearum was mainly related to sugar metabolism and photosynthesis.