盐胁迫与适盐生防菌Bacillus sp. B268对木麻黄青枯病的协同抑制机制

The bacterial wilt disease can infect a wild range of plants, and thus, is quite difficult to be controlled. By now, less research on the wilt disease control of forest trees has been reported. However, seawater irrigation, a method which takes use of the salt resistance of host plant, has been well practiced in China in controlling the bacterial wilt of Casuarina. Based on this background, a novel halophilic Bacillus strain, designated B268, was isolated from the seawater irrigation area and was found to be active in inhibition the wilt pathogen. This program is subjected to focus on the synergistic mechanism of salt stress and strain B268 on controlling the wilt disease in Casuarina. The responses of Casuarina to the salt stress at the levels of resistant physiology reactions and resistance signals transduction, as well as the responses of strain B268 to the salinity at the levels of physiological activities in growth-promoting and transcriptional activities of functional genes are both researched, for the purpose to elucidate the molecular mechanism of the synergistic induction of Casuarina resistance by salt stress and strain B268, which also exhibit a synergistic inhibition of the wilt pathogen. All responsive genes and their transcriptional regulations shall be illuminated. Aims of this program is to explore the mechanism of salt tolerance in Casuarina and to interpret the effect of this characteristic on disease controlling, in addition, to dig up the potentials of halophilic biocontrol bacteria applied in the saline environments, and thus, to supply a novel idea for the disease control of other salt tolerant plants. In conclusion, it is worthy in both research and practice.

青枯病寄主范围广，防治难度大，尤其在林木青枯病方面，研究报道较少。而海水浇淋利用寄主木麻黄的耐盐性进行青枯病的防治，在我国已有一定的实践基础。以此为据，本项目以一株分离自海水浇淋区的适盐青枯病拮抗细菌Bacillus sp. B268为材料，探讨其与盐胁迫对木麻黄青枯病的协同抑制机制。主要从抗逆生理反应以及抗逆信号传导两个方面解析木麻黄对盐胁迫的应答，从促生生理活性和基因转录活性两个方面探讨菌株B268对盐的响应，进而探明盐胁迫以及生防菌在协同拮抗病原菌的基础之上，协同诱导木麻黄抗性的分子机制，包括过程中的各应答基因及其转录调控。本项目旨在探索木麻黄的耐盐机制及其在病害防治中的作用，挖掘适盐生防菌在盐渍化环境中的应用潜力，并为其他耐盐植物的病害防治提供新的思路，具有一定的研究意义和应用潜力。

芽孢杆菌类植物根际细菌能够以多种机制促进植物在生物和非生物胁迫下的生长，是一类重要的生物防治资源。本项目以一株分离自木麻黄根部的适盐芽孢杆菌B268为对象，以一株新报道的I-16序列型木麻黄青枯病原菌YQ为靶标，探讨B268在生防活性、基因转录以及互作应答方面对盐的响应特性，结果表明，在一定范围的盐胁迫条件下，B268的表观促生活性和功能基因转录均上调，响应范围为1-3%NaCl，同时在根际接种条件下，B268能够降低宿主的盐敏感性，并在高盐胁迫时，降低宿主胞内的渗透压和氧化压力，减少结构损伤，提高抗逆性。经鉴定，B268属于同种贝莱斯芽孢杆菌单系群，与群内其他成员间具有一定的表型和基因型差异，耐盐和抑菌范围广，能在响应盐胁迫的同时有效抑制青枯病原菌，适用于盐渍化环境中生防菌与植物间的互作促生和抗病机制研究，以及广适盐生防菌剂的应用开发。