Combined bacterial and mycorrhizal inocula improve tomato quality at reduced fertilization

Plant Growth Promoting Bacteria (PGPB) and Arbuscular Mycorrhizal Fungi (AMF) can positively affect plant nutrition and growth. Recent studies have also shown that rhizospheric microorganisms can result in improved fruit features. Aim of this work was to evaluate, in an industrial farming, the effects of three selected biostimulants (consisting of a mix of Plant Growth Promoting Bacteria and Arbuscular Mycorrhizal Fungi), employed in conditions of reduced fertilization on yield, fruit quality and nutritional value. Tomato plants were inoculated with AM fungi and Pseudomonas sp. 19Fv1T or P. fluorescens C7, transplanted and grown in open field under conditions of reduced fertilization. The impact of the microorganisms on the fruit yield and nutritional value was assessed by measuring the production, fruit size and concentration of soluble sugars, organic acids, carotenoids and ascorbate. The size and biomass of tomato fruits were affected by the inocula. Sugar concentration was increased by the selected microorganisms. All the mixtures induced an enhancement of malic acid, while double colonization with AMF and PGPB increased β-carotene concentration in fruits if compared to controls. The results of the present study show that inoculation with soil microorganisms can help to drastically reduce the use of chemical fertilization, maintaining and, in some cases, even improving the tomato fruit yield and quality. This can lead to economical, environmental and human health benefits in relation to the increased sustainability.