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چکیده
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An endophytic bacterial strain, isolated from Fragaria × ananassa roots, and its antifungal activity against Colletotrichum nymphaeae was investigated under in vitro, in vivo, and greenhouse experiments. Bacterial isolate was identified as Bacillus atrophaeus strain DM6120 using phenotypic, biochemical and molecular phylogenetic analysis of the 16S rDNA gene sequences. Bacterial strain DM6120 suppressed mycelial growth of C. nymphaeae (54.92%) using dual-culture method. The non-volatile compounds produced by DM6120 inhibited mycelial growth and conidial germination of C. nymphaeae by 74.12% and 80.80%, respectively. However, inhibition percentage of mycelial growth of the pathogen by volatile compounds of the strain DM6120 was lower (11.9%) than that for the two dual culture and non-volatile compounds tests. The strain DM6120 produced protease, chitinase, pectinase, siderophore, IAA, gibberellin, and fixed nitrogen. The living cells of the strain DM6120 decreased anthracnose disease at post-harvest on fruit by 71.42%. Furthermore, disease severity of strawberry anthracnose was suppressed using soil drenching and foliar spray application methods 60 days after inoculation by 94.44% and 88.88%, respectively. PCR amplification confirmed the presence of iturin and surfactin genes in strain DM6120. The bioactive fractions produced by strain DM6120 were analyzed by Gas Chromatography-Mass Spectroscopy. Six compounds from n-butanol extract and seven compounds from methanol extract were identified. 1,1-Dibutoxyacetone (58.789%) and Diethylene glycol, o,o-di(pivaloyl)- (29.922%) from n-butanol extract and acetic acid (39.923%) and 2-Furanmethanol (30.305%) from methanol extract were determined as the main bioactive compounds produced by bacterial strain DM6120.
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