Biosafe Management of Botrytis Grey Mold of Strawberry Fruit by Novel Bioagents

Abstract

Recently, there have been urgent economic and scientific demands to decrease the use of chemical fungicides during the treatment of phytopathogens, due to their human health and environmental impacts. This study explored the biocontrol efficacy of novel and eco-friendly preen (uropygial) oil and endophytic Bacillus safensis in managing postharvest Botrytis grey mold in strawberry fruit. The preen oil (25 μL/mL) showed high antifungal activity against B. cinerea Str5 in terms of the reduction in the fungal radial growth (41.3%) and the fungal colony-forming units (28.6%) compared to the control. A new strain of Bacillus safensis B3 had a good potential to produce chitinase enzymes (3.69 ± 0.31 U/mL), hydrolytic lipase (10.65 ± 0.51 U/mL), and protease enzymes (13.28 ± 0.65 U/mL), which are responsible for the hydrolysis of the B. cinerea Str5 cell wall and, consequently, restrict fungal growth. The in vivo experiment on strawberry fruit showed that preen (uropygial) oil reduced the disease severity by 87.25%, while the endophytic bacteria B. safensis B3 reduced it by 86.52%. This study reports the efficiency of individually applied bioagents in the control of phytopathogenic fungi for the first time and, consequently, encourages their application as a new and innovative strategy for prospective agricultural technology and food safety.

Keywords: Bacillus safensis; Botrytis cinerea; innovative strategy; postharvest disease; preen (uropygail) oil; strawberry.

Figure 1

Botrytis cinerea Str5—the causal agent of strawberry grey mold disease.

Figure 2

Scanning electron micrographs illustrating a comparison between healthy strawberry fruit and those infected with B. cinerea Str5. Healthy strawberry fruit show a smooth surface without fungal colonization (A,B); however, the infected fruit (C,D) show the intensive occurrence of hyphae on the fruit surface.

Figure 3

Impacts of different concentrations of preen oil on B. cinerea Str5 growth in terms of colony-forming units. Vertical bars represent the standard error (n = 3). Columns followed by the same letter are not significantly different at p < 0.05.

Figure 4

Impacts of different concentrations of preen oil on B. cinerea radial growth. Vertical bars represent the standard error (n = 3). Columns followed by the same letter are not significantly different at p < 0.05.

Figure 5

GC/MS profile of preen oil composition.

Figure 6

Antagonistic activities of isolated endophytic bacteria against B. cinerea Str5. Vertical bars represent the standard error (n = 3). Columns followed by the same letter are not significantly different at p < 0.05.

Figure 7

Phylogenetic tree of the most antagonistic bacterial strain B3. The strain is aligned in the clade with B. safensis, with 100% similarity. The evolutionary history was inferred using the UPGMA method. The evolutionary distances were computed using the maximum composite likelihood method, and are in the units of the number of base substitutions per site.

Figure 8

Fruit treatments with preen oil and/or Bacillus safensis B3 compared with untreated fruit (healthy control) and fruit infected only with B. cinerea Str5 (infected control).

Figure 9

Effects of different treatments on total phenols in strawberry fruit. Vertical bars represent the standard error (n = 3). Columns followed by the same letter are not significantly different at p < 0.05.

Figure 10

Effects of different treatments on antioxidant activities of superoxide dismutase (SOD) (A), catalase (CAT) (B), ascorbate peroxidase (APX) (C), and peroxidase (PO) (D) in strawberry fruit. Vertical bars represent the standard error (n = 3). Columns followed by the same letter are not significantly different at p < 0.05.