Frikha-Gargouri Olfa, Ben Abdallah Dorra, Bhar Ilhem, Tounsi Slim
Biopesticides Laboratory, Centre of Biotechnology of Sfax, Sfax UniversitySfax, Tunisia.
Front Plant Sci. 2017 Aug 14;8:1363. doi: 10.3389/fpls.2017.01363. eCollection 2017.
This study aimed to improve the screening method for the selection of biocontrol agents against crown gall disease. The relationship between the strain biocontrol ability and their studied traits was investigated to identify the most important factors to be considered for the selection of effective biocontrol agents. In fact, previous selection procedure relying only on antibacterial activity was shown to be not suitable in some cases. A direct plant-protection strategy was performed to screen the 32 biocontrol agent candidates. Moreover, potential biocontrol traits were investigated including biofilm formation, motility, hemolytic activity, detection of lipopeptide biosynthetic genes ( and ) and production of antibacterial compounds. The obtained results indicated high correlations of the efficiency of the biocontrol with the reduction of gall weight ( = 0.000) and the antibacterial activity ( = 0.000). Moreover, there was strong correlations of the efficiency of the biocontrol ( = 0.004) and the reduction in gall weight ( = 0.000) with the presence of the gene. This gene directs the synthesis of the lipopeptide bacillomycin belonging to the iturinic family of lipopeptides. These results were also confirmed by the two-way hierarchical cluster analysis and the correspondence analysis showing the relatedness of these four variables. According to the obtained results a new screening procedure of biocontrol agents against crown gall disease could be advanced consisting on two step selection procedure. The first consists on selecting strains with high antibacterial activity or those harbouring the gene. Further selection has to be performed on tomato plants . Moreover, based on the results of the biocontrol assay, five potent strains exhibiting high biocontrol abilities were selected. They were identified as or . These strains were found to produce either surfactin or surfactin and iturin lipopeptides. In conclusion, our study presented a new and effective method to evaluate the biocontrol ability of antagonistic strains against crown gall disease that could increase the efficiency of screening method of biocontrol agents. Besides, the selected strains could be used as novel biocontrol agents against pathogenic strains.
本研究旨在改进用于筛选防治冠瘿病生物防治剂的方法。研究了菌株的生物防治能力与其所研究性状之间的关系，以确定筛选有效生物防治剂时需考虑的最重要因素。事实上，先前仅依靠抗菌活性的筛选程序在某些情况下并不适用。采用直接的植物保护策略对32种生物防治剂候选菌株进行筛选。此外，还研究了潜在的生物防治性状，包括生物膜形成、运动性、溶血活性、脂肽生物合成基因（和）的检测以及抗菌化合物的产生。所得结果表明，生物防治效率与瘿瘤重量减轻（=0.000）和抗菌活性（=0.000）高度相关。此外，生物防治效率（=0.004）和瘿瘤重量减轻（=0.000）与基因的存在密切相关。该基因指导合成属于iturin家族脂肽的脂肽杆菌霉素。双向层次聚类分析和对应分析也证实了这些结果，显示了这四个变量之间的相关性。根据所得结果，可以提出一种针对冠瘿病生物防治剂的新筛选程序，该程序包括两步选择过程。第一步是选择具有高抗菌活性的菌株或携带基因的菌株。进一步的筛选必须在番茄植株上进行。此外，根据生物防治试验结果，选择了5株具有高生物防治能力的强效菌株。它们被鉴定为或。发现这些菌株产生表面活性素或表面活性素和iturin脂肽。总之，我们的研究提出了一种新的有效方法来评估拮抗菌株对冠瘿病的生物防治能力，这可以提高生物防治剂筛选方法的效率。此外，所选菌株可作为对抗致病菌株的新型生物防治剂。
