Enhanced shelf-life of the formulated biocontrol agent Bacillus amyloliquefaciens CPA-8 combining diverse packaging strategies and storage conditions

Two effective biocontrol products (named as BA3 and BA4) based on Bacillus amyloliquefaciens CPA-8 have been reported as a potential alternative to chemical applications against brown rot caused by Monilinia spp. on stone fruit. To have practical use, this study aimed to describe the best packaging strategies (bags or flasks, atmosphere, and temperature of storage) to not only guarantee efficacy but also stability and ease of application of the products to be handled through the normal channels of distribution and storage. In terms of the viability neither the BA3 nor the BA4 product has been compromised after twelve months of storage. However, storage at 4 °C affected the stability and visual aspect of both CPA-8 formulations, mainly associated not only to the increase of RH but also aw. Moreover, it should be pointed out that flasks did not conserve refrigerated BA3 samples in a suitable way, since RH and aw increased noticeably making their visual properties unsightly after 10 months of cold storage. At that time, the BA4 products were better preserved at 4 °C when packaged in flasks. Finally, this study also demonstrated that the most suitable packaging conditions for long-term storability (stored at 22 °C) did not show any negative effect in the biocontrol efficacy of CPA-8 in nectarines artificially infected with M. fructicola and provide suitable product delivery and field application. In conclusion, these results contribute to the final stage of development of these two CPA-8 products, practically ready for registration, thus contributing to the environmental-friendly management of postharvest diseases in stone fruit.info:eu-repo/semantics/acceptedVersio

Antifungal effect of volatile organic compounds produced by Bacillus amyloliquefaciens CPA-8 against fruit pathogen decays of cherry

The present work focuses on the antifungal effect of volatile organic compounds (VOCs) produced by Bacillus amyloliquefaciens CPA-8 against Monilinia laxa, M. fructicola and Botrytis cinera, three postharvest fruit pathogens of sweet cherry fruit. VOCs were evaluated with a double petri dish assay against mycelial and colony growth of target pathogens. For this purpose, CPA-8 was grown on different media and cultured for 24 and 48 h at 30 °C before assays. Data showed that mycelial growth inhibition was higher when CPA-8 was grown on Tryptone Soya Agar (TSA) while no differences were generally observed when CPA-8 was cultured for either, 24 and 48 h. Moreover, no effects were observed on colony growth. The main volatile compounds emitted by CPA-8 were identified by solid-phase microextraction (SPME)-gas chromatography as 1,3 pentadiene, acetoin (3-hydroxy-2-butanone) and thiophene. Pure compounds were also tested in vitro on mycelial growth inhibition and their EC50 values against the three pathogens were estimated. Thiophene was the most effective VOC, showing more than 82% suppression of mycelial growth at the highest concentration (1.35 μL/mL headspace) and EC50 values ranging from 0.06 to 6.67 μL/mL headspace. Finally, the effectiveness of thiophene and CPA-8 VOCs was evaluated against artificially inoculated cherry fruits. Among the target pathogens, M. fructicola was clearly controlled by CPA-8 with less than 25% of rotten fruits compared to the control (65% disease incidence) and for all pathogens, less than 37.5% of CPA-8 treated decayed fruits produced spores (disease sporulation). Otherwise, pure thiophene showed no effect against any pathogen on disease incidence and disease sporulation. The results indicated that VOCs produced by B. amyloliquefaciens CPA-8 could develop an additive antifungal effect against postharvest fruit pathogens on stone fruit.This research was supported by the European project BIOCOMES FP7-612713 and by the Catalan government (Generalitat de Catalunya) for the PhD grant 2016-FI-B2 00143 (Amparo M. Gotor)