Biocontrol Ability and Mechanism of a Broad-Spectrum Antifungal Strain Bacillus safensis sp. QN1NO-4 Against Strawberry Anthracnose Caused by Colletotrichum fragariae

Abstract

Strawberry is a very popular fruit with a special taste, color, and nutritional value. Anthracnose caused by Colletotrichum fragariae severely limits fruit shelf life during post-harvest storage. Use of traditional chemical fungicides leads to serious environment pollution and threatens food safety. Biocontrol is considered as a promising strategy to manage the post-harvest fruit diseases. Here, strain QN1NO-4 isolated from noni (Morinda citrifolia L.) fruit exhibited a high antifungal activity against C. fragariae. Based on its physicochemical profiles and phylogenetic tree of the 16S rRNA sequence, strain QN1NO-4 belonged to the genus Bacillus. The average nucleotide identity (ANI) calculated by comparing two standard strain genomes was below 95–96%, suggesting that the strain might be a novel species of the genus Bacillus and named as Bacillus safensis sp. QN1NO-4. Its extract effectively reduced the incidence of strawberry anthracnose of harvested fruit. Fruit weight and TSS contents were also maintained significantly. The antifungal mechanism assays indicated that the extract of the test antagonist inhibited mycelial growth and spore germination of C. fragariae in vitro. Cells of strain QN1NO-4 demonstrated the cytoplasmic heterogeneity, disappeared organelles, and ruptured ultrastructure. Notably, the strain extract also had a broad-spectrum antifungal activity. Compared with the whole genome of strain QN1NO-4, several functional gene clusters involved in the biosynthesis of active secondary metabolites were observed. Fifteen compounds were identified by gas chromatography–mass spectrometry (GC-MS). Hence, the fruit endophyte B. safensis sp. QN1NO-4 is a potential bio-agent identified for the management of post-harvest disease of strawberry fruit.

Native Cultivable Bacteria from the Blueberry Microbiome as Novel Potential Biocontrol Agents

“…Studies on combined, possibly synergistic actions are in progress. The compelling antagonistic capacities of B. velezensis BA3 and BA4 agree with a number of literature reports focusing on biocontrol capabilities of species belonging to the genus Bacillus , which excel in their ability to produce a wide range of bioactive antimicrobial substances such as lipopeptides, antibiotics, enzymes, polyketides, and non-ribosomal proteins [ 36 , 41 , 42 , 43 ]. Since the members of the genus are characterized by their ability to produce heat, drought, and solvent-tolerant endospores, they are, with respect to durability, almost ideally suited for their inclusion in biocontrol formulations [ 44 , 45 ].…”

“…The dual culture assay in our study again proved successful as a valuable qualitative approach to quickly assess antagonistic activities of microorganisms directed at fungal postharvest phytopathogens [ 25 , 33 , 34 , 35 , 36 ].…”

Characterization of a broad-spectrum antifungal strain, Streptomyces graminearus STR-1, against Magnaporthe oryzae

“…For instance, the efficacy of fermentation broth of Streptomyce F2 on inhibiting the growth of anthracnose fungus of peppers was decreased at temperatures above 70°C ( Jiang and Song, 2015 ). In addition, the biocontrol activity of fermentation extract of Streptomyce H4 was maintained under ultraviolet light and strong alkaline conditions but was decreased under high temperatures and strong acid conditions ( Li et al, 2021a , b ). Unlike these previous findings, our study revealed that the fermentation extract of biocontrol strain STR-1 maintained high antifungal activity at temperatures ranging from 40°C to 130°C and exhibited stability within the pH range of 2.0 to 12.0 ( Supplementary Figure S1 ).…”

A Biocontrol Strain of Serratia plymuthica MM Promotes Growth and Controls Fusarium Wilt in Watermelon

“…These compounds inhibit the synthesis of functional proteins by down-regulating specific functional protein coding genes [31,57,58]. 2,5-Piperazinedione, 3-methyl-6-(1-methylethyl)-and 2,5-Piperazinedione, 3,6-bis(2-methylpropyl)are found in many strains of Bacillus and have been reported to exhibit strong antifungal activity against various phytopathogenic fungi [31,[59][60][61][62]. Additionally, 9-octadecenamide, (Z) has also been reported to possess antimicrobial properties [63,64].…”