Role of plant associated microbiota in fruit aroma and plant defense in strawberry and raspberry

The study of plant-associated microbiomes is a rapidly growing field of extraordinary interest. In the last few years, an increasing number of functions has been attributed to the microbiome associated to crop plants, including the promotion of host growth, the induction of resistance and the protection against abiotic and biotic stress. Some research has also focused on the contribution of the microbial community to fruit quality. Pioneer studies dealt with the influence of the association between Methylobacterium strains and strawberries to the composition of the aroma of fruit. In this study, the fruit-associated microbiome of different strawberry and raspberry cultivars was characterized by a metagenomic approach, based on the sequencing of the 16S gene on Illumina platform. The profile of volatile organic compounds (VOCs) of the same fruits was previously characterized by PTR-Tof-MS and GCMS to describe the main chemical components of the berry aroma and the data were correlated to the presence and abundance of microbial species capable of producing VOCs of interest. For the bacterial strains belonging to such species, the growth rates on the fruit and the production of VOCs were measured in order to quantify their contribution to the aroma composition of the fruit. In addition, the metagenomic exploration highlighted the presence of bacterial species potentially acting as biological control agents (BCAs) or as plant-growth promoting bacteria (PGPB). Their populations were quantified by QPCR in various organs of the plant beside the fruit. Putative BCAs were tested against pathogens, on both plants and fruits in postharvest condition. The ultimate/last aim of the present work was to identify useful bacteria in the resident microbiome of some valuable crop plants, in order to design a sustainable orchard management strategy, integrating crop associated functional microbes as one of the key components.