Genome Association Analysis Of Resistance To Peanut Web Blotch And Cytology Study On The Mechanism Of Resistance

As an important economic crop,peanut(Arachis hypogaea L.)is infected by various foliar diseases.The web blotch disease,caused by Phoma arachidicola,is one of the most serious peanut foliar diseases,which harms peanut leaves and reduces yield.In order to excavate peanut web blotch resistance resources and reveal the mechanism of peanut leaf spot resistance,firstly,peanut natural populations were identified by in door inoculation,and a number of peanut web blotch resistance associated sites were excavated by genome-wide association analysis.Cytological observation was carried out on different types of resistance responses of the identified resistance materials through microscopic observation.In this study,the natural population composed of 353 peanut germ plasms was used to identify the resistance to web blotch disease.42 varieties with high resistance and 33 varieties with high susceptibility were selected,among which Yuanza 9847 and Jinong 99 were the most resistant varieties which disease index was 10.19.The most susceptible peanut variety was Yiya,and its disease index was 98.15.According to the analysis of disease index of different plant types,it was found that the disease resistance of var.hirsuta was stronger than that of the others include var.vulgaris,var.hypogaea and var.fastigiata(p < 0.05).Using genome-wide association analysis,eleven SNPs loci related to web blotch resistance were found.These SNPs loci were distributed on 8 chromosomes of peanut,among which SNP with the highest value of-log10(P)was located on chromosome10.31 candidate genes related to web blotch disease resistance were screened out near the related SNPs loci,including cytochrome P450 superfamily protein genes,signal molecular genes with PPR structure,NBS-LRR disease resistance genes and transcription factors related to disease resistance,etc.In this study,resistant varieties Zheng 8903,Yuhua 15 and susceptible varieties Wuyou 7,Yuhua 4 were selected for cytological study to explore the infection process of peanut web blotch pathogen and the resistant physiological response of peanut.The results were as follows: there was no significant difference in the germination rate of conidia among peanut varieties with different resistance,but the frequency of appressorium formation was different.The appressorium formation frequency of resistant varieties was lower than that of susceptible varieties.Papillae reaction and hypersensitive response appeared in all four varieties,but the frequency of papillae formation and hypersensitive response in resistant varieties was higher than those in susceptible varieties.The formation frequency of papillae reaction was significantly negatively correlated with the disease index(p<0.01),the correlation coefficient was0.68,and the hypersensitive response formation frequency was significantly negatively correlated with the disease index(p<0.01),and the correlation coefficient was 0.91.Based on the statistics of effective resistance responses of different resistant peanut varieties at 48 h and 84 h after inoculation,it was found that only the frequency of effective papillae formation and effective hypersensitive response of resistant varieties were increased.