嫁接樱桃通过根系分泌物防控根癌病的机制研究

The production of cherry is facing great challenge from crown gall disease caused by Agrobacterium tumefaciens. Grafting using a high resistant plant as the root stock has been shown to be an efficient way to control crown gall disease, for instance, crown gall disease incident of the “Hongdeng” cherry could be decreased by grafting onto the rootstock of “Haiying 1” cherry. Grafting is known to affect the root exudates of plant, which has been shown to be the most important regulating factor of rhizosphere microbiome. However, the compound(s) in root exudates of grafted plants that regulates rhizosphere microbiome and mediates the decrease of crown gall disease of cherry plant has not been studied. In this research, two different cultivars of cherry, the high resistant cultivar “Haiying 1” and the weak resistant cultivar “Hongdeng” against Agrobacterium tumefaciens, will be grafted onto each other. The root exudates of the grafted plant will be collected and analyzed by Gas Chromatography-Mass Spectrometer (GC-MS). Meanwhile，the root exudates from different grafted plants will be applied to disease soil. Subsequently, the microbiome of the soil treated with different root exudates will be analyzed and correlated with the compounds in root exudates. Thereby we could identify the key compound(s) in root exudates that influences the richness of the soil-borne pathogen, and by a further step, the role of this compound in interaction between the grafted plant and the microbiome would be studied. Finally, we expect to explain how root exudates mediate the enhancement of resistance of grafted plant against Agrobacterium tumefaciens. This work would show a deep understand of the mechanism of controlling soil-borne disease by grafting, and theoretically support the control of cherry crown gall disease by regulating rhizosphere microbiome.

根癌农杆菌引起的根癌病对樱桃生产具有严重危害。以抗性较强的植物作为砧木进行嫁接是一种有效防治植物根癌病的方法，如“海樱1号”作为砧木嫁接甜樱桃“红灯”可显著降低根癌病发病率。嫁接会改变植物根系分泌物，而分泌物能调节根际微生物群落。然而嫁接植物根系分泌物中调控土壤微生物群落以抵抗根癌病的物质或类群仍不明了。本项目拟用对根癌病抗性较强的“海樱1号”和抗性较弱的“红灯”樱桃互作砧木进行嫁接，通过气象色谱-质谱联用技术对不同嫁接模式的植物根系分泌物进行分析。同时将分泌物添加至发病土，利用高通量测序检测土壤微生物群落的变化。对根系分泌物组分和微生物群落结构相关性分析，筛选根系分泌物中影响根癌农杆菌丰度的活性物质，并探究该物质在嫁接植物和根际微生物群落互作中的作用。阐述嫁接植物通过根系分泌物降低根癌病的机制。本研究有助于深入认识嫁接防控土传病害的机理，并为通过调控果树根际微生物防控根癌病提供理论指导。

根癌农杆菌引起的根癌病对樱桃生产具有严重危害。以抗性较强的植物作为砧木进行嫁接是一种有效防治植物根癌病的方法。申请人发现用抗病能力较强的“海樱1号”作为砧木嫁接培育抗病能力较弱的“吉塞拉”能够显著降低土壤中的致病性根癌农杆菌的丰度。申请人进一步研究发现根系分泌物和根际微生物群落变化是导致根癌农杆菌丰度降低的关键因素。申请人鉴定到一株对致病性根癌农杆菌C58具有拮抗作用的根际益生芽孢杆菌CLA178，并且发现其产生的聚酮类化合物macrolactin是主要的抑菌物质；申请人还发现根系分泌物中的缬氨酸是调控根癌农杆菌C58趋化性、生物膜形成、根际丰度的关键信号分子，而降低缬氨酸能够降低根癌农杆菌的丰度以及根癌病的发病。本研究有助于深入认识嫁接防控土传病害的机理，为减少根癌病造成的樱桃生产损失提供理论指导。