香蕉林土壤可培养放线菌分离、鉴定及其抑菌活性

Isolation, identification, and antimicrobial activity of culturable Actinomycetes from banana plantation soil

摘要:

【背景】香蕉枯萎病是香蕉的顽固性疾病，制约着香蕉产业的发展，因此，筛选出对香蕉枯萎病菌(尖孢镰刀菌古巴专化型4号生理小种，简称Foc4)具有抑制活性的生防菌株具有重要意义。【目的】分离香蕉林土壤样品中放线菌并进行物种的初步鉴定，测定其对包括香蕉枯萎病致病菌的7种病原菌的拮抗活性，获得高活性菌株，以获得解决香蕉枯萎病的生物防治策略。【方法】采集多份广西地区香蕉林土壤样品，采用超声波等手段对其预处理，设置多种特异性培养基从中分离放线菌资源，对获得的放线菌进行基于16S rRNA基因序列的物种鉴定，以7种病原菌为靶标，采用平板对峙法从中筛选抑菌活性菌株，最后采用菌丝生长速率法对Foc4的抑菌率进行测定。【结果】从香蕉林土壤中分离出138株放线菌均为链霉菌，其中5株为潜在新种，分别为X1085、X1052、X2052、X3059和X4046；筛选出具有抑菌活性的菌株77株，阳性率为55.8%。20株对Foc4具有抑制活性，其中4株拮抗效果明显，抑制率大于80%，菌株X4050的抑菌率高达93.76%。【结论】初步明确了香蕉林土壤中可培养放线菌的物种信息，其中部分放线菌为未知物种，活性分析显示一半以上的菌株具有抗菌生物活性，一部分对香蕉枯萎病病菌具有良好的拮抗活性。该研究结果可为香蕉林土壤可培养放线菌的分离、鉴定、生物活性研究提供理论依据，为香蕉枯萎病的生物防治提供思路。

Abstract:

[Background] Panama disease of banana, an intractable disease in banana, restricts the development of banana industry. Therefore, it is of great significance to screen out strains with inhibitory activity against Fusarium oxysporum f. sp. cubense tropical race 4 (Foc4). [Objective] To isolate Actinomycetes from samples of banana plantation soil and preliminarily identify species, and subsequently determine the antagonistic activities of the isolated Actinomycetes against seven pathogens including Foc4, so as to acquire strains with high activity and biological control strategies to solve Panama disease of banana. [Methods] Soil samples of banana plantation soil in Guangxi were collected and pretreated by ultrasonic wave and other means. Actinomycetes were separated using a variety of specific media and identified based on their 16S rRNA gene sequences. Seven pathogenic bacteria were used as targets to screen out the bacteriostatic strains by the plate confrontation method, and the bacteriostatic rate against Foc4 was determined by the mycelial growth rate method. [Results] A total of 138 strains of Actinomycetes were isolated from the samples of banana plantation soil, all of which were Streptomyces. Among them, five strains numbered X1085, X1052, X2052, X3059, and X4046 were potential new species. Seventy-seven strains with antimicrobial activities were screened out, with the positive rate of 55.8%. Twenty strains exhibited inhibitory activity against Foc4, among which four strains manifested obvious antagonistic effects, and their inhibitory rates were greater than 80%. The inhibitory rate of the strain X4050 was 93.76%. [Conclusion] The species information of culturable Actinomycetes in banana plantation soil was preliminarily clarified, and some of them were unknown species. Results of activity analysis showed that more than half of Actinomycetes had antimicrobial activity, and some of them exhibited good antagonistic activity against Foc4. These results provide a theoretical basis for the research on the isolation, identification, and biological activity of culturable Actinomycetes in the banana plantation soil, and provide a new idea for biological control of Panama disease of banana.