Exploration Of Specific Gene(s) For Ear Rot Resistance In Maize

Maize ear rot,as a common fungal maize disease,globally occurs in the maize-growing domain.Currently,most inbred lines applied to maize breeding worldwide generally lack resistance to ear rot.In recent years,the number of studies on the resistance of ear rot is continually growing along with the augment of the frequency of maize ear rot.Whereas,most of them mainly focus on Fusarium verticilloides,and the efficiency of maize ear rot resistance is relatively low.In addition,fine mapping of maize ear rot resistance genes has not been reported.In this study,using genom-wide association analysis(GWAS)approach based on two dominant pathogenic pathogens [Fusarium verticilloides(Fv)and Fusarium graminearumin(Fg)] of maize ear rot,we conducted investigation to explore specific resistant gene(s)of maize ear rot including field inoculation methods,resistence assessment of maize germplasm and ultimately the resistant gene identification.The results are as follows:First,we compared 11 commonly used pathogenic inoculation approaches,and revealed that maize spore solution and mung Bean spore solution performed better than the rest of inoculation methods tested.Second,we assessed ear rot resistance of 44 maize inbred lines from different heterotic groups that were inoculated with two dominant pathogenic pathogens for two cultivative seasons.The results showed that TangSiPingTou group exhibited highly sensitive(HS),while LvDaHongGu group showed highly resistant(HR)to ear rot.However,Raid group behaved dvengent resistance to maize ear rot.Among all inbred lines of the 5 groups,FaA and Ye81162 showed HR and HS respectively against infections of two dominant pathogenic pathogens,and were successively used for further investigation.Furthermore,using the HR(FaA)and the HS(Ye81162)inbred lines identified above,we carried out differentially gene expression analyses.The results showed that the function of the differentially expressed genes included pathogen recognition,signaling,defense,and the pathway involved defense responses mediated by WRKY transcription factors and hormons like jasmonic acid and ethylene.Moreover,we adopted 527 inbred maiz from tropical,subtropical and temperate regions to carried out GWAS analysis on maize ear rot resistance two dominant pathogenic pathogens.The result showed that a total of 13 SNPs for Fv resistance and 95 SNPs for Fg resistance were identified respectively.The genes associated with above SNPs are encoding kinases,auxin,plant defensins,transcription factors and so on.In addition,we performed an associated analysis in the combined output of both the transcriptome and GWAS.One differentially expressed gene encoding an intrinsicmembrane protein from the Fv-induced transcriptome was consistent with a locus revealed by GWAS.Whilst,in the Fg-induced transcriptome,13 differentially expressed genes were co-incident with GWAS results,among which 7 genes encode functional proteins,6 genes are related to enzyme synthesis and 1 gene encodes a proliferating cell nuclear antigen.In this study,we identified a few important resistant gene candidates associating with the infection of Fg and Fv.Fine mapping of these genes is in progress in our group.The current findings are of insights into exploration of maize disease resistant mechanism and indeed maize breeding.