大豆种质对细菌性斑疹病不同菌株抗性的遗传解析

Soybean bacterial pustule disease can occur seriously under high temperature and high humidity condition in main soybean production regions worldwide. There is pathogenicity differentiation of the pathogen Xanthomonas axonopodis pv. glycines (Xag), so it is necessary to conduct the research work on the genetics and breeding of soybean resistance to pustule. The disease is epidemic in south of Huang-Huai river valley and southern China, However, little is known about the pathogenicity differentiation of the pathogen, and identification of elite resistant resources and their genetic base should be deeply studied. In the present proposal, we hypothesize that there might be different genetic loci in soybean germplasm conferring resistance to pustule under the pressure of pathogenicity differentiation. The corresponding research contents include three points. 1) To collect and classify the strains of Xag from different regions in China, and reveal their distribution and molecular characters. 2) To investigate the resistance reaction of soybean germplasm population with more than 900 genotypes to reveal the genetic variation of the sample, and dissect the QTL architecture for the resistance to different strains through linkage mapping and association analysis. 3) Fine mapping and functional analysis of the major resistance QTL/genes, and constructing the regulating network system of responding differential expression genes to the infection of pathogenic bacteria. In all, we try to reveal the genetic base of soybean resistance to bacterial pustule by combining the results from the QTL, related key genes and pathway studies. It can provide a new research model for the interaction between bacteria and host, and extend the genetics and breeding research of soybean disease resistance through discovery of the resistant gene germplasm and establishment of the efficient work platform for bacterial pustule.

大豆细菌性斑疹病是世界性病害，在高温高湿条件下发病重，在我国黄淮南部及南方大豆产区常见。其致病菌地毯草黄单孢杆菌大豆致病变种存在致病力分化，目前对该病菌多样性及大豆抗病基因资源了解不多。我们假设在斑疹病菌株致病力分化压力下大豆种质应存在不同的抗病基因，据此拟开展以下研究：①对我国大豆产区细菌性斑疹病的致病菌进行菌株划分，研究其分布特点与分子特性；②研究国内外大豆种质资源群体(>900份)对斑疹病不同菌株的抗性反应，揭示抗病性遗传变异特点，并通过连锁和关联定位全面揭示大豆种质对不同菌株抗性的QTL构成；③对抗病主效QTL进行精细定位和功能分析，研究应答病原菌侵染的基因调控体系。最终从QTL、关键基因、代谢通路等层面揭示大豆抗斑疹病遗传体系，为解析细菌-寄主互作系统提供新实例；同时发掘大豆抗病基因资源，建立抗斑疹病高效技术体系，拓展我国大豆抗病遗传育种工作。

由地毯草黄单胞杆菌大豆致病变种Xanthornonas axonopodis pv. glycines（Xag）引起的大豆细菌性斑疹病（Bacterial Leaf Pustule, BLP）最高可造成50%的减产，在温暖湿润的地区容易发生，是世界性病害。目前对我国大豆BLP病原菌多样性及大豆抗病基因资源了解不多。本课题开展了大豆细菌性斑疹病菌不同菌株遗传差异、大豆种质对斑疹病不同病菌抗性反应的遗传变异特点、大豆种质对斑疹病抗性QTL解析、大豆抗斑疹病病基因发掘与功能等方面研究。主要进展包括：1）从各地采集的359份病叶样本中分离出81个大豆BLP病原菌分离物，并将12个代表性Xag菌株分为2个致病力不同的类群，并揭示了B1、T8二个菌株在基因组序列等方面的差异；2）对国内外大豆种质资源进行接种C5、B1、T8等3个Xag菌株的抗病性鉴定，筛选出一批抗病种质资源，大豆对不同菌株抗性存在差异反应。3）连锁与关联定位鉴定到8个抗C5菌株的主要染色体区段；对江淮大豆育种种质群体人工喷雾接种B1、T8菌株，检测到24个与抗性显著相关的QTN，其中位于17号染色体的区段在3个菌株接种和自然发病条件下均检测到，Gm06_2745725为抗B1和T8新位点。利用四引物ARMS-PCR方法设计特异性引物对与rxp显著关联的QTN Gm17_7307486进行基因分型，可用于大豆BLP抗性育种。4）利用抗感亲本测序与单倍型分析、过表达和CRISPR/Cas9系统对Glyma.17G090400、Glyma.17G090200等基因进行了功能分析。同时优化qPCR技术检测Xag侵染条件下抗病候选基因在BLP抗感品种中的表达水平，发现作为柑橘溃疡病感病基因CsLOB1的同源基因，大豆2个差异表达基因Glyma.17G086300和Glyma.05G040500可能参与了BLP抗性调控。5）发表论文28篇，参编英文专著1章，申请专利1项。