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.

扣球菌引起的炭疽病是日本草莓最具破坏力的疾病之一，尤其是在夏季的保育期。在这项研究中，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。从经过表面消毒的草莓组织中成功分离出总共226种放线菌。在第一次筛选中，使用分离小叶分析研究了226种放线菌分离物中的217种对草莓炭疽病的抑制作用。发现分离物MBFA-172和MBFA-227显着抑制炭疽病病变的发展。然后在受控环境室内的两个月大的草莓塞苗上测试了两种分离物的功效。发现分离物MBFA-172提供了一致的疾病抑制，因此被选作在温室实验中进一步评估的最终候选者。结果表明，与未处理的对照组相比，用分离的MBFA-172处理可显着降低草莓炭疽病的严重程度和发病率。因此，由MBFA-172提供的疾病控制功效在统计学上可与化学杀真菌剂propineb相比。使用自发抗硫链球菌突变株MBFA-172的自发突变株进行的重新分离实验表明，在喷雾处理后，该菌株有效地定居了草莓植物的地上组织至少三周。将文化，形态和生理学测试与基于16S rRNA的分子分析相结合，与热链霉菌相关的物种。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。