Dhar Purkayastha Gargee, Mangar Preeti, Saha Aniruddha, Saha Dipanwita
Department of Biotechnology, University of North Bengal, Siliguri, West Bengal, India.
Department of Botany, University of North Bengal, Siliguri, West Bengal, India.
PLoS One. 2018 Feb 21;13(2):e0191761. doi: 10.1371/journal.pone.0191761. eCollection 2018.
The aim of the present study is to evaluate plant growth promoting and biocontrol efficacy of a Serratia marcescens strain ETR17 isolated from tea rhizosphere for the effective management of root rot disease in tea. Isolated bacterial culture ETR17 showed significant level of in vitro antagonism against nine different foliar and root pathogens of tea. The phenotypic and molecular characterization of ETR17 revealed the identity of the bacterium as Serratia marcescens. The bacterium was found to produce several hydrolytic enzymes like chitinase, protease, lipase, cellulase and plant growth promoting metabolites like IAA and siderophore. Scanning electron microscopic studies on the interaction zone between pathogen and antagonistic bacterial isolate revealed severe deformities in the fungal mycelia. Spectral analyses (LC-ESI-MS, UV-VIS spectrophotometry and HPLC) and TLC indicated the presence of the antibiotics pyrrolnitrin and prodigiosin in the extracellular bacterial culture extracts. Biofilm formation by ETR17 on polystyrene surface was also observed. In vivo application of talc-based formulations prepared with the isolate ETR17 in tea plantlets under green house conditions revealed effective reduction of root-rot disease as well as plant growth promotion to a considerable extent. Viability studies with the ETR17 talc formulation showed the survivability of the isolate up to six months at room temperature. The sustenance of ETR17 (concentration of 8-9x108 cfu g-1) in the soil after the application of talc formulation was recorded by ELISA. Safety studies revealed that ETR17 did not produce hemolysin as observed in pathogenic Serratia strains. The biocontrol strain reported in this study can be used for field application in order to minimize the use of chemical fungicides for disease control in tea gardens.
本研究的目的是评估从茶树根际分离得到的粘质沙雷氏菌菌株ETR17对促进植物生长和生物防治的效果，以有效管理茶树根腐病。分离得到的细菌培养物ETR17对九种不同的茶树叶部和根部病原体表现出显著的体外拮抗作用。ETR17的表型和分子特征表明该细菌为粘质沙雷氏菌。发现该细菌能产生几种水解酶，如几丁质酶、蛋白酶、脂肪酶、纤维素酶，以及促进植物生长的代谢产物，如吲哚-3-乙酸（IAA）和铁载体。对病原体与拮抗细菌分离物之间相互作用区域的扫描电子显微镜研究显示，真菌菌丝体出现严重变形。光谱分析（液相色谱-电喷雾电离质谱、紫外-可见分光光度法和高效液相色谱）和薄层色谱表明，细胞外细菌培养提取物中存在抗生素吡咯菌素和灵菌红素。还观察到ETR17在聚苯乙烯表面形成生物膜。在温室条件下，将用分离物ETR17制备的滑石粉制剂在茶苗上进行体内应用，结果表明能有效减轻根腐病，并在很大程度上促进植物生长。对ETR17滑石粉制剂的活力研究表明，该分离物在室温下可存活长达六个月。通过酶联免疫吸附测定（ELISA）记录了滑石粉制剂施用后ETR17（浓度为8-9×10⁸ cfu g⁻¹）在土壤中的留存情况。安全性研究表明，ETR17不像致病性粘质沙雷氏菌菌株那样产生溶血素。本研究报道的生物防治菌株可用于田间应用，以尽量减少茶园中用于病害防治的化学杀菌剂的使用。
