广西香蕉细菌性软腐病病原鉴定及生物学特性研究

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摘要 为明确引起广西香蕉细菌性软腐病的病原，采用组织分离法从染病的香蕉组织中分离病原菌，通过柯赫氏法则验证其致病性。对病原菌进行形态学观察、分子鉴定、生理生化测试及生物学特性测定。结果表明，从染病蕉头和蕉果分离到的病原菌，其菌株的形态特征、生理生化测试结果与Dickeya sp.基本一致，16S rDNA基因序列与Dickeya 属细菌的同源性达99%;其最适培养温度为28℃，最适pH为7.0。病原菌的dnaX、gryB和recA基因序列与D. zeae的同源性均在97%以上。多基因系统发育树显示，病原菌与所有的D. zeae细菌聚在同一个最小进化分支里，自展支持率为100%。根据以上结果，将引起广西香蕉细菌性软腐病的病原菌鉴定为Dickeya zeae。同时，测定7种杀菌剂对GR-1菌株的室内毒力，46%氢氧化铜WG的EC50最低，为186.69 mg/L; 其500倍稀释液对GR-1菌株的抑菌效果最好，达76.89%。

关键词 香蕉; Dickeya zeae; 病原鉴定; 多基因系统发育; 生物学特性

中图分类号： S 436.681  文献标识码： A  DOI： 10.16688/j.zwbh.2018413

Abstract In order to clarify the pathogen causing banana bacterial soft rot in Guangxi， the pathogenic bacteria were isolated by tissue separation method from tissues of diseased banana， and their pathogenicity were verified through Koch’s Rule. The pathogen was identified based on morphology， physiological and biochemical characteristics， molecular identification and biological characteristics. The results showed that the pathogenic bacteria were isolated from the pseudostem and fruit of diseased bananas. Their morphological characteristics， physiological and biochemical results were basically consistent with Dickeya sp.， and the 16S rDNA gene sequences shared 99% similarity with that of Dickeya sp.. The optimum temperature for the pathogenic bacterium was 28℃， and the optimum pH was 7.0. The homology of dnaX， gryB and recA gene sequences between the pathogenic bacterium and D. zeae was more than 97%. Multiple-gene phylogenetic analyses indicated that the pathogen and all the bacteria of D. zeae clustered in the same evolutionary branch， with a self-supporting rate of 100%. According to these results， the pathogen causing banana bacterial soft rot in Guangxi was identified as Dickeya zeae. Furthermore， the toxicity of 7 types of bactericides against strain GR-1 were tested. The EC50 of copper hydroxide 46% WG was the lowest among the tested bactericides （186.69 mg/L）， and its 500 times dilution had the best inhibition effect on GR-1 strain， up to 76.89%.

Key words banana; Dickeya zeae; pathogen identification; multiple-gene phylogeny; biological characteristics

香蕉是我國南亚热带地区的特色作物，也是广西重要的经济作物。2016年起，陆续在广西玉林、北海等市县的蕉园发现一种新型病害，可侵染‘金粉’、‘广粉’和‘威廉斯’等香蕉主栽品种，主要危害香蕉球茎和生长点，导致假茎软腐发臭，叶片发黄，严重时整株倒伏和死亡。此外，该病害在田间亦可感染蕉果，导致果实由内而外变褐腐烂，造成蕉果发育缓慢，果指细小，往往其果皮颜色与健果无多大区别，但果肉内已发生明显褐变或腐烂。该病害在香蕉苗期至成株期均可发生，并呈逐渐上升的趋势，部分蕉园发病率达20%，病死率达70%。高温多雨、地表温度高和田间排水不畅造成园间积水等会加速该病害的发生和流行。国内外已报道的危害香蕉假茎的病害有：由尖孢镰刀菌古巴专化型Fusarium oxysporum f.sp. cubense引起的香蕉枯萎病、由青枯菌Ralstonia solanacearum引起的香蕉细菌性枯萎病、由菊欧文氏菌Erwinia chrysanthemi引起的香蕉细菌性软腐病、由黄瓜花叶病毒香蕉株系Cucumber mosaic virus banana strain引起的香蕉花叶心腐病、由香蕉束顶病毒Banana bunchy top virus （BBTV）引起的香蕉束顶病等;危害蕉果的病害有：由芭蕉炭疽菌Colletotrichum musae引起的香蕉炭疽病、由轮纹镰孢Fusarium concentricum引起的香蕉冠腐病、由香蕉大茎点霉Macrophoma musae引起的香蕉黑星病以及由可可轮枝孢Verticillium theobromae引起的香蕉烟头病等[1-5]。然而，目前对广西田间发生的既危害香蕉植株，同时又危害香蕉果实的这种新病害，在国内尚未见相关报道，也不明确其病原菌的分类地位。因此，对该病害的病原菌进行鉴定与分类，是有效防治该病害的基本前提。为明确该病害的病原，本研究通过对染病的香蕉假茎和蕉果进行组织分离，以柯赫氏法则验证病原的致病性，并对其进行形态学观察、分子生物学鉴定、生理生化测试及生物学特性测定，以期为该病害的有效防治提供理论依据。