Marian Malek, Ohno Teppei, Suzuki Hirofumi, Kitamura Hatsuyoshi, Kuroda Katsutoshi, Shimizu Masafumi
Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.
Faculty of Bioresources, Mie University, Mie 514-8507, Japan.
Microbiol Res. 2020 Feb 7;234:126428. doi: 10.1016/j.micres.2020.126428.
Anthracnose caused by Glomerella cingulata is one of the most devastating diseases of strawberry in Japan, particularly during its nursery period in the summer. In this study, we aimed to isolate and screen endophytic actinobacteria, to identify potential biocontrol agents capable of suppressing strawberry anthracnose. A total of 226 actinobacteria were successfully isolated from surface-sterilized strawberry tissues. In the first screening, 217 out of 226 actinobacteria isolates were studied for their suppression effect on strawberry anthracnose using a detached leaflet assay. It was discovered that isolates MBFA-172 and MBFA-227 markedly suppressed the development of anthracnose lesions. The efficacy of both isolates was then tested on two-month-old strawberry plug seedlings in a controlled environmental chamber. It was found that isolate MBFA-172 provided consistent disease suppression and was thus selected as a final candidate for further evaluation in a glasshouse experiment. Results showed that the severity as well as incidence rate of strawberry anthracnose was significantly reduced by treatment with isolate MBFA-172 compared with that of untreated control. Accordingly, the disease control efficacy provided by MBFA-172 was statistically comparable to the chemical fungicide propineb. A re-isolation experiment using a spontaneous thiostrepton-resistant mutated strain of isolate MBFA-172 revealed that it efficiently colonized the above-ground tissues of strawberry plants for at least three weeks after spray treatment. Using cultural, morphological, and physiological tests combined with 16S rRNA-based molecular analysis, MBFA-172 was identified as a moderately thermophilic Streptomyces thermocarboxydus-related species. Upon review, our results strongly indicated that MBFA-172 is a promising biocontrol agent for strawberry anthracnose.
由围小丛壳菌引起的炭疽病是日本草莓最具毁灭性的病害之一，尤其是在夏季育苗期。在本研究中，我们旨在分离和筛选内生放线菌，以鉴定能够抑制草莓炭疽病的潜在生物防治剂。从表面消毒的草莓组织中成功分离出226株放线菌。在第一次筛选中，使用离体小叶试验研究了226株放线菌分离物中的217株对草莓炭疽病的抑制作用。发现分离物MBFA - 172和MBFA - 227显著抑制了炭疽病病斑的发展。然后在可控环境室中对两个月大的草莓穴盘苗测试了这两种分离物的效果。发现分离物MBFA - 172能持续抑制病害，因此被选为在温室试验中进一步评估的最终候选菌株。结果表明，与未处理的对照相比，用分离物MBFA - 172处理可显著降低草莓炭疽病的严重程度和发病率。因此，MBFA - 172提供的病害防治效果在统计学上与化学杀菌剂丙森锌相当。使用分离物MBFA - 172的自发硫链丝菌素抗性突变菌株进行的再分离实验表明，喷雾处理后它能在草莓植株的地上组织中有效定殖至少三周。通过培养、形态和生理测试结合基于16S rRNA的分子分析，MBFA - 172被鉴定为与嗜热链霉菌相关的中度嗜热物种。经审查，我们的结果强烈表明MBFA - 172是一种有前途的草莓炭疽病生物防治剂。
