Aims: A Bacillus amyloliquefaciens strain, surviving epiphytically on the surface of fruit, was isolated while searching for naturally occurring biological control agents. This bacterial strain was characterized for its antifungal activity against seven selected fungal postharvest pathogens of citrus. Methods and Results: To understand the antifungal activity, seven postharvest fungal pathogens were screened for growth inhibition by B. amyloliquefaciens strain. Assays using B. amyloliquefaciens lipopeptide extracts showed a strong inhibitive activity. The inhibitory effect was observed in abnormal conidial germination and germ tube development when conidia were treated with different lipopeptide extract concentrations. Further analysis using PCR and chromatography confirmed the presence of fengycin, iturin and surfactine, of which iturin A showed the strongest and most common inhibitory effect. The results are supported by site-directed mutagenesis analysis, targeted to suppress the biosynthesis of iturin A production. Fruit trials confirmed disease development inhibition when the antagonist was applied 1 day prior to or 1 day after fungal application. Conclusions: We conclude that the iturin family of lipopeptides are vital in the antagonism of B. amyloliquefaciens against the seven citrus postharvest pathogenic fungi tested. Significance and Impact of the Study: We elucidated the principal mechanism used by B. amyloliquefaciens PPCB004 to suppress postharvest disease development on stored fruits.

Microbes play an important role in plants and interact closely with their host starting from sprouting seeds, continuing during growth and after harvest. The discovery of their importance for plant and postharvest health initiated a biotechnological development of various antagonistic bacteria and fungi for disease control. Nevertheless, their application often showed inconsistent effects. Recently, high-throughput sequencing-based techniques including advanced microscopy reveal fruits and vegetables as holobionts. At harvest, all fruits and vegetables harbor a highly abundant and specific microbiota including beneficial, pathogenic and spoilage microorganisms. Especially, a high microbial diversity and resilient microbial networks were shown to be linked to fruit and vegetable health, while diseased products showed severe dysbiosis. Field and postharvest handling of fruits and vegetables was shown to affect the indigenous microbiome and therefore has a substantial impact on the storability of fruits and vegetables. Microbiome tracking can be implemented as a new tool to evaluate and assess all postharvest processes and contribute to fruit and vegetable health. Here, we summarize current research advancements in the emerging field of postharvest microbiomes and elaborate its importance. The generated knowledge provides profound insights into postharvest microbiome dynamics and sets a new basis for targeted, microbiome-driven and sustainable control strategies.

Avocados are a popular subtropical fruit of high economic importance, and the European Union is the biggest importer of the bulk of the fruit coming from countries such as South Africa, Chile, and Israel. The fruit is highly nutritious, being rich in vitamins A, B, C, minerals, potassium, phosphorus, magnesium, iron, and antioxidants. The biggest challenge is that the fruit is highly susceptible to qualitative and quantitative postharvest losses. Successful maintenance of avocado fruit quality during the supply chain depends on many aspects, including adequate orchard management practices, harvesting practices, packing operations, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are mostly attributed to flesh softening, decay, physiological disorders, and improper temperature management. Management of the supply chain is solely done to provide the fruit with the most favorable conditions to extend storage life, and retain quality and nutritional attributes of the fruit. The focus of this review is therefore to study the findings that have emanated from research done to retain overall avocado fruit quality and to reduce postharvest losses during the supply chain through the adoption of appropriate and novel postharvest technologies.