中国农业科学 ›› 2023, Vol. 56 ›› Issue (18): 3642-3654.doi: 10.3864/j.issn.0578-1752.2023.18.012

• 园艺 • 上一篇    下一篇

宽皮柑橘褐斑病抗性的全基因组关联分析

杨胜男(), 程莉, 谈月霞, 朱延松, 江东()   

  1. 西南大学柑桔研究所,重庆 400712
  • 收稿日期:2023-02-14 接受日期:2023-05-04 出版日期:2023-09-16 发布日期:2023-09-21
  • 通信作者:
    江东,E-mail:
  • 联系方式: 杨胜男,E-mail:y_sn@qq.com。
  • 基金资助:
    国家重点研发计划(2019YFD1001400); 柑橘种质资源精准鉴定(19211142)

Genome Wide Association Study for Resistance to Citrus Brown Spot Disease

YANG ShengNan(), CHENG Li, TAN YueXia, ZHU YanSong, JIANG Dong()   

  1. Citrus Research Institute of Southwest University, Chongqing 400712
  • Received:2023-02-14 Accepted:2023-05-04 Published:2023-09-16 Online:2023-09-21

摘要:

目的】挖掘宽皮柑橘褐斑病抗性基因及抗病资源中的相关基因型,为柑橘品种抗褐斑病改良提供依据。【方法】在夏秋两季对136份宽皮柑橘离体叶片进行褐斑病病菌接种试验,将两次试验结果取交集,得到121份宽皮柑橘的褐斑病感抗结果。用121份宽皮柑橘表型对前人开发的CAPS进行验证,再对这121份宽皮柑橘的表型结果与利用简化基因组获得的SNP基因型结果进行主成分分析、GWAS分析和Fst分析,获得宽皮柑橘褐斑病抗性相关SNP位点。对通过GWAS获得的SNP进行基因型分析,在所有候选SNP的上下游25 kb范围内选取候选基因,根据phytozome注释对候选基因进行筛选。在感病资源‘秤砣红橘’和抗病资源‘新克里曼丁’接种褐斑病病菌24、48和72 h后,利用实时荧光定量PCR对筛选出的基因进行表达量分析。【结果】发现在121份宽皮柑橘中,温州蜜柑和克里曼丁类等67份资源表现抗褐斑病,大部分红橘和椪柑等54份资源感褐斑病。本研究发现前人开发的CAPS准确率为76.86%,其相关性为中等程度相关。以-log10(P)>4.5为标准,GWAS筛选出6个强关联SNP;以Fst>0.38为标准,Fst筛选出8个SNP。GWAS筛选出的6个SNP的基因型与宽皮柑橘抗褐斑病表现为强相关,其中位于3号染色体上24 838 146 bp位置处Ciclev10021676的SNP1基因型对宽皮柑橘抗褐斑病区分能力最强。从14个SNP中筛选出Ciclev10018604Ciclev10023485Ciclev10023486Ciclev10024586Ciclev10019874等5个基因。这5个基因在‘秤砣红橘’接种病原菌后表达量上调,且都在48 h后表达量达到最高,上调倍数高达90倍。【结论】通过GWAS挖掘出3号染色体上24 838 146 bp位置的SNP与宽皮柑橘褐斑病抗病性相关性最显著,相关系数为0.641。并且该位置的基因型能比较有效地将抗性资源和感病资源进行区分。挖掘到Ciclev10019874Ciclev10018604Ciclev10023485Ciclev10024586Ciclev10023486等5个调控宽皮柑橘抗褐斑病的候选基因。

关键词: 宽皮柑橘, 褐斑病, 分子标记, 全基因组关联分析, 群体遗传分化指数分析

Abstract:

Objective】The study objective was to explore candidate genes associated with resistance to Alternaria brown spot disease in citrus mandarin, so as to provide the basis for developing suitable molecular markers for further citrus resistance breeding work. 【Method】In summer and autumn of 2022, the young leaves of 136 citrus mandarin accessions were picked and inoculated with the fungus mycelium of Alternaria alternata in the laboratory. The combined results of two experiments were used to obtain the reliable results of 121 citrus mandarins responding to Alternaria brown spot. The phenotypes of 121 citrus mandarins were selected to verify the effectiveness of the CAPS marker developed in a previous study. Then, in order to obtain the candidate SNPs related to Alternaria brown spot resistance, the phenotypes of 121 citrus mandarins and corresponding SNP genotype data from GBS sequencing were analyzed with PCA, GWAS, and Fst methods, respectively. Candidate genes had been selected from the flanking region of 25 kb sequences surrounding the candidate SNPs site, and then they were screened out according to phytozome annotations. The expressions of candidate genes were analyzed after inoculating with the pathogen fungus on leave of Chengtuo hongju and Clementina (Algeria) for 24, 48, and 72 h. 【Result】Among 121 citrus mandarins, 67 varieties such as Clementine and Satsuma were resistant to Alternaria brown spot disease, whereas 54 varieties such as Hong Ju and Ponkan were susceptible. Some varieties resistance to Alternaria brown spot disease could discriminated by CAPS, but its accuracy only accounted for 76.86% in the study. GWAS analysis identified six significant SNPs highly associated with disease resistance, among which SNP1 located in Ciclev10021676 at 24 838 146 bp of chromosome 3 could be used to predicate the resistance of varieties, and their genotype showed a strong correlation with phenotype. Eight significant SNPs highly associated with disease resistance selected by Fst analysis. Finally, five genes of Ciclev10018604, Ciclev10023485, Ciclev10023486, Ciclev10024586 and Ciclev10019874 were screened out. The expression levels of these five genes in Chengtuo Hongju were up-regulated extensively after inoculating leaves with the pathogen fungus, and their expression levels reached the highest 48 hours later. 【Conclusion】Through GWAS, the SNP at 24 838 146 bp on chromosome 3 was found to be the most significant one with high resistance correlation to Alternaria brown spot disease, and the genotype at this location could be effectively used to distinguish the resistant varieties. The candidate genes responding to Alternaria brown spot disease in mandarin were discussed, i.e., Ciclev10019874, Ciclev10018604, Ciclev10023485, Ciclev10024586, and Ciclev10023486.

Key words: citrus mandarin, Alternaria brown spot, molecular marker, genome-wide association study, fixation index