Isolation and Characterization of Bacillus velezensis Strain P2-1 for Biocontrol of Apple Postharvest Decay Caused by Botryosphaeria dothidea

Abstract

Botryosphaeria dothidea causes apple ring rot, which is among the most prevalent postharvest diseases of apples and causes significant economic loss during storage. In this study, we investigated the biocontrol activity and possible mechanism of Bacillus velezensis strain P2-1 isolated from apple branches against B. dothidea in postharvest apple fruit. The results showed strain P2-1, one of the 80 different endophytic bacterial strains from apple branches, exhibited strong inhibitory effects against B. dothidea growth and resulted in hyphal deformity. B. velezensis P2-1 treatment significantly reduced the ring rot caused by B. dothidea. Additionally, the supernatant of strain P2-1 exhibited antifungal activity against B. dothidea. Re-isolation assay indicated the capability of strain P2-1 to colonize and survive in apple fruit. PCR and qRT-PCR assays revealed that strain P2-1 harbored the gene clusters required for biosynthesis of antifungal lipopeptides and polyketides. Strain P2-1 treatment significantly enhanced the expression levels of pathogenesis-related genes (MdPR1 and MdPR5) but did not significantly affect apple fruit qualities (measured in fruit firmness, titratable acid, ascorbic acid, and soluble sugar). Thus, our results suggest that B. velezensis strain P2-1 is a biocontrol agent against B. dothidea-induced apple postharvest decay. It acts partially by inhibiting mycelial growth of B. dothidea, secreting antifungal substances, and inducing apple defense responses.

Biocontrol Ability of the Bacillus amyloliquefaciens Group, B. amyloliquefaciens, B. velezensis, B. nakamurai, and B. siamensis, for the Management of Fungal Postharvest Diseases: A Review

“…9,68 B. amyloliquefaciens SF14 and SP10 not only produced antifungal lipopeptides bacillomycin, fengycin, iturin, and surfactin but also lytic enzymes with amylase, protease, and cellulase activities (Figure 1B), 125 whereas B. velezensis P2-1 was able to synthesize lipopeptides and polyketides and simultaneously induce disease resistance in postharvest apples. 126 This indicates that some strains can simultaneously use different mechanisms of action. Sawant et al reported that B. amyloliquefaciens DRo-198 and TS-204 were able to produce enzymes with cellulase, β-1,3-glucanase, and chitinase activities.…”

Biocontrol activity and action mechanism of Paenibacillus polymyxa strain Nl4 against pear Valsa canker caused by Valsa pyri

“…The V. pyri, Valsa mali, C. gloeosporioides and Botryosphaeria dothidea strains used for the present study (Yuan et al, 2022) were cultured in potato dextrose agar (PDA; potato extracts 200 g L −1 , glucose 20 g L −1 , and agar 15 g L −1 ) and grow at 25°C.…”

“…Healthy one-year-old branches were harvested in June 2021 from an "Enli" pear tree in Zhengzhou (Henan province, China) to isolate endophytic bacteria with the procedure as the same as reported previously (Yuan et al, 2022). The ability of all isolated endophytes to inhibit the growth of V. pyri was assessed using a dual culture screening approach as detailed previously by Yuan et al (2022).…”

“…Healthy one-year-old branches were harvested in June 2021 from an "Enli" pear tree in Zhengzhou (Henan province, China) to isolate endophytic bacteria with the procedure as the same as reported previously (Yuan et al, 2022). The ability of all isolated endophytes to inhibit the growth of V. pyri was assessed using a dual culture screening approach as detailed previously by Yuan et al (2022). Briefly, after overnight culture in LB broth (peptone 10 g L −1 , yeast extract 5 g L −1 , and sodium chloride 10 g L −1 ), 3 μl of bacteria were inoculated on PDA medium on each side of a Petri dish (2 cm from the center), with a mycelial plug (diameter: 5 mm) being placed in the center of this plate.…”

“…Several different endophyte have been reported to be effective agents in the bicontrol of pear Valsa canker, such as Bacillus subtilis, Bacillus velezensis, Bacillus amyloliquefaciens, Lysobacter enzymogenes, and Penicillium citrinum (Cheng et al, 2017;Song et al, 2020;Liu R. et al, 2021;Yu et al, 2021;Yuan et al, 2021). Bacillus velezensis strains D4 and P2-1, for example, can readily inhibit V. pyri growth (Liu R. et al, 2021;Yuan et al, 2022), while B. subtilis strain 168-produced dipicolinic acid (DPA) can exert antifungal activity through the suppression of chitin synthesis (Song et al, 2020). Despite these promising results, the availability of biocontrol agents in preventing pear Valsa canker remains limited, hampering the effective control of this disease in agronomic practice.…”