Abstract: Konjac(Amorphophallus konjac)is a horticultural plant with high nutritional and medicinal values. Soft rot is a severe disease in production of konjac and it is also the main factor restricting the development of the konjac industry. It has been reported that the soft rot of konjac is mainly caused by pathogenic bacteria(mainly including Pectobacterium aroidearum, P. carotovorum subsp. carotovorum, P. chrysanthemi and Enterobacter sp.), and there is rare reports on pathogenic fungi that cause konjac soft rot. In order to clarify the pathogenic types and infection characteristics of the soft rot in Qujing City, Yunnan Province, the diseased corms were collected for fungal isolation by tissue isolation methods. The isolated fungi were identified by morphological and molecular identification methods based on ITS and LSU sequence analyses, and pathogenicity was determined according to Koch's rule. The infection characteristic was analyzed by mixed inoculation using the identified pathogenic fungi and the pathogenic bacteria of konjac soft rot. The results were as follows:(1)Three species of Fusarium spp.(Fusarium concentricum, F. oxysporum and F. ambrosium), one species of Mucor sp., one species of Rhizopus sp., one species of Penicillium sp. and one species of Clonostachys sp. were identified.(2)Statistics analysis found that Fusarium concentricum had the highest relative abundance(45.45%).(3)Koch postulates tests showed that inoculation with F. concentricum caused obvious soft rot symptoms of konjac corms within three days.(4)In addition, mixed Pectobacterium aroidearum and Fusarium concentricum together inoculation promoted the disease development, and the weight of rotten tissue was significantly higher than that of single inoculation using F. concentricum or Pectobacterium aroidearum. Overall, these results indicate that konjac soft rot may be caused by a combination of fungus and bacterium infection. The results provide a theoretical reference for the prevention and management of konjac soft rot.

Key words: Amorphophallus konjac, soft rot, pathogenic fungus, phylogenetic analysis, pathogenicity

摘要： 魔芋软腐病是魔芋生产过程中的重要病害,也是限魔芋产业发展的主要因素。目前,已有报道魔芋软腐病主要由细菌引起,鲜有真菌引起魔芋球茎软腐发病的报道。为明确云南曲靖市花魔芋(Amorphophallus konjac)软腐病的病原种类和侵染特征,该研究通过组织分离法,对采集自云南曲靖市的花魔芋病样进行了真菌的分离,通过形态学结合基于ITS与LSU序列分析的分子鉴定方法对分离真菌进行鉴定,并根据柯赫氏法则进行致病性测定,并对鉴定出的病原真菌同魔芋软腐病原细菌进行了双回接试验分析。结果表明:(1)从形态学和分子水平鉴定了轮纹镰刀菌(Fusarium concentricum)、尖孢镰刀菌(F. oxysporum)和F. ambrosium 3种镰刀菌,1种毛霉属真菌(Mucor sp.),1种根霉属真菌(Rhizopus sp.),1种青霉属真菌(Penicillium sp.)和1种粉红螺旋聚孢霉属真菌(Clonostachys sp.)。(2)统计分析发现,轮纹镰刀菌的相对丰度最高,为45.45%。(3)柯赫氏法则检测发现轮纹镰刀菌具有致病性。(4)轮纹镰刀菌和病原细菌胡萝卜果胶杆菌(Pectobacterium aroidearum)双接种魔芋球茎发现软腐病发病更快,病变组织重量显著高于单接种轮纹镰刀菌或果胶杆菌处理。综上表明,魔芋软腐病可能是由真菌和细菌合侵染引发。该研究结果为魔芋软腐病的防治提供了理论依据。

关键词: 花魔芋, 软腐病, 病原真菌, 系统发育分析, 致病性