玉米镰孢菌复合病原茎腐病抗性种质资源鉴定及抗性基因挖掘

Identification of Resistant Germplasms and Mining of Candidate Genes Associated with Resistance to Stalk Rot Caused by Synergistic Infection with Fusarium spp.in Maize

【目的】玉米茎腐病是我国玉米主产区普遍发生的重要病害之一,自然条件下,玉米茎腐病多由多种病原菌共同侵染造成。筛选抗禾谷镰孢菌(Fusarium graminearum)和拟轮枝镰孢菌(Fusarium verticillioides)复合侵染的优异玉米种质,鉴定与复合病原引起的茎腐病抗性相关数量性状核苷酸(quantitative trait nucleotide,QTN),挖掘抗性候选基因,为玉米抗复合病原抗性分子育种提供基因资源和理论借鉴。【方法】以一个玉米自然群体为试验材料,接种F.graminearum和F.verticillioides复合病原菌,鉴定茎腐病表型;利用全基因组关联分析,筛选显著抗性SNP位点,预测抗病候选基因。【结果】通过田间和室内2个环境下接种复合病原后的茎腐病表型鉴定试验,发现不同来源和亚群的自交系对复合病原侵染的表型差异显著。田间表型鉴定结果表明,收集于中国的自交系普遍抗性较高,而美国的自交系普遍感病性较高;热带及亚热带亚群的自交系抗性较高,混合型亚群的自交系感病性较高。室内表型鉴定结果表明,收集于美国的自交系材料抗性较高,国际玉米小麦改良中心的自交系材料感病性高;硬秆亚群的玉米种质表现较高抗性,混合型亚群的种质表现较高感病性。于田间和室内2个环境下分别筛选出29份和16份对复合病原侵染具有较高抗性水平的种质,2个环境共同筛选到6份抗病种质。基于田间表型GWAS分析,鉴定到18个与复合病原茎腐病抗性显著相关的QTN,挖掘出93个抗病候选基因;有4个基因表现出单倍型变异,且接种后基因表达水平在抗病材料中呈上调趋势。【结论】利用遗传背景丰富的玉米自然群体,在2个环境中共同鉴定出6份玉米镰孢菌复合病原茎腐病抗性材料,可作为潜在的玉米抗茎腐病育种种质资源;挖掘出4个可能参与复合病原菌抗性的候选基因,为玉米镰孢菌复合病原茎腐病抗性育种提供基因资源。

【Objective】Maize stalk rot is one of the common and most devastating diseases in major maize production areas in China.Under natural conditions,maize stalk rot is mostly caused by the synergistic infection of various pathogens.The purpose of this study was to screen elite maize germplasms resistant to the synergistic infection with F.graminearum and F.verticillioides.Meanwhile,QTN associated with resistance to the infection by synergistic infection of two Fusarium species and the candidate resistance genes were identified,which will provide gene resources and theoretical reference for molecular breeding of maize variety resistant to synergistic infection of different pathogens.【Method】Using a maize natural population as experimental materials,the maize stalk rot phenotypes were investigated upon simultaneous infection with F.graminearum and F.verticillioides.Furthermore,GWAS analysis was conducted to identify significant resistance SNP and to predict candidate genes for stalk rot resistance.【Result】Through the phenotypic analysis of stalk rot caused by synergistic infection under both field and laboratory conditions,it was found that inbred lines from different sources and subgroups showed significant phenotypic variation.More specifically,the field assay results showed that the inbred lines collected from China were more resistant and that from USA were more susceptible to synergistic infection.Moreover,the inbred lines of tropical and subtropical subgroup were more resistant,whereas the inbred lines of Mixed subgroup more susceptible.The seedling assay results under laboratory condition showed that the lines collected from USA were more resistant,whereas that from CIMMYT were more susceptible.The lines of SS subgroup were more resistant,and that of Mixed subgroup were more susceptible.By integrating field and laboratory phenotypic data,29 and 16 lines with higher levels of resistance to synergistic infection were screened out respectively,and 6 resistant lines were identified under both conditions.Moreover,based on the field phenotype GWAS,18 QTNs associated with the resistance were identified,and 93 candidate genes associated with stalk rot resistance to synergistic infection were mined.Among these candidate genes,four genes showed haplotype variation,whose expression levels were up-regulated in disease-resistant lines.【Conclusion】Using the natural population of maize with great diversity in genetic background,6 resistant lines to the synergistic infection with Fusarium spp.were identified under two conditions,which can be used as potential germplasm resources for maize stalk rot resistance in the future.Four candidate genes that might be involved in the resistance to synergistic infection were identified by GWAS,which will provide genetic resources for the breeding maize varieties with enhanced resistance to stalk rot caused by F.graminearum and F.verticillioides.