Biological control of brown rot in stone fruit using Bacillus amyloliquefaciens CPA-8 under field conditions

Abstract

Different treatments based on the biocontrol agent (BCA) Bacillus amyloliquefaciens CPA-8 to control brown rot under field conditions were evaluated as alternative to chemical applications. As part of a well-designed disease program that enables the integration of BCAs into cropping systems, testing of the sensitivity of Monilinia laxa and Monilinia fructicola at different doses of CPA-8 were conducted in stone fruit. CPA-8 dose of 10 7 CFU mL-1 reduced more than 60.0 and 75.5 % of brown rot incidence and severity, respectively. Once in the orchard, different degree of biocontrol activity was obtained depending on the inoculum pressure, which was mainly associated with meteorological conditions. Under drastic disease pressure, neither CPA-8 treatment nor the chemicals controlled the disease at harvest and only the chemical treatment reduced postharvest brown rot incidence. However, when Monilinia spp. incidence was close to the standard levels recorded in the area, treatments based on CPA-8 formulations proved to be efficacious. At harvest, BA3, BA4 treatments (CPA-8 optimised products) and PF+BA3 treatment (CPA-8 combined with Penicillium frequentans) reduced Monilinia spp. incidence compared to the control (54.7-64.1 %) although less than the chemicals (90.6 %). At postharvest, almost all CPA-8-based treatments (except PF+BA3) controlled the pathogen with BA4 treatment being as much effective as the chemicals (50.3 % of disease reduction). Finally, the population dynamics of CPA-8 on treated fruit surface remained after treatment application, at harvest and at postharvest shelf-life (>10 4 CFU cm-2). This study highlights the potential of B. amyloliquefaciens CPA-8 as alternative or complementary strategies to control Monilinia spp.

Environmental fate and behaviour of the biocontrol agent Bacillus amyloliquefaciens CPA‐8 after preharvest application to stone fruit

“…The efficacy of preharvest and postharvest applications of the BCA B. amyloliquefaciens CPA‐8 to control brown rot in stone fruit has already been demonstrated . However, to ensure its efficacy after field treatment, it is necessary to know the ecological fitness of this bacterium, which is determined by the physical and microbiological environment .…”

“…alone or in combination with other postharvest treatments . Moreover, recent studies revealed that applications of B. amyloliquefaciens during the preharvest of peaches and nectarines substantially reduced brown rot decay during postharvest …”

Biocontrol of Postharvest Fruit Fungal Diseases by Bacterial Antagonists: A Review

“…Numerous microbial antagonists of postharvest phytopathogens have been identified in laboratory and field studies and exploited commercially [12]. To date, the development of products based on beneficial microorganisms is relevant to reducing chemical contaminants in the food supply [80].…”

Compatibility interactions between the biocontrol agent Penicillium frequentans Pf909 and other existing strategies to brown rot control

“…In other hand, control efficacy achieved by a combination of BCAs exhibiting different mechanisms of biocontrol may also result in antagonistic, additive or synergistic effects (Guetsky et al, 2002(Guetsky et al, , 2001. Bacillus amyloliquefaciens CPA-8 has been reported as an effective antagonist against preharvest (Gotor-Vila et al, 2017a), and postharvest brown rot caused by Monilinia spp. based mainly on its capability of production of powerful antifungal metabolites such us fengycinlike lipopeptides and other mechanisms of action such as competition and production of volatiles The combination of different mechanisms of action, competition by Pf909 and antibiosis or volatiles by CPA8, could improve brown rot biocontrol obtained by each one.…”