Microbiota from ‘next-generation green compost’ improves suppressiveness of composted Municipal-Solid-Waste to soil-borne plant pathogens

Biological control of soil-borne plant pathogenic fungi using compost from organic-waste as soil amendment has been proposed as an effective strategy in crop protection in the past years. In this study, the pathogen-specific property of commercial composts to suppress Fusarium oxysporum f. sp. melonis wilt on melon has been enhanced transferring the multi-suppressive properties from seven ‘next-generation green composts’ made of agro-industrial residues and plant green-waste, including the steam-explosion liquid wastes derived from a 2nd-generation fuel ethanol production chain, into two composts made of Municipal-Solid-Waste (MSW) and one made of cow manure-household waste. After determination either of the physical-chemical features and suppressive properties of the starting composts, either of the taxonomic structure and biological-enzymatic properties of the microbial consortia derived from them, the objective of this work has been reached recruiting the microbial consortia into an industrial composting cycle. A total of twenty-one tailor-made composts were tested for the suppressive properties into a nursery soil-less system under greenhouse condition using plant growing media container amended with 30% (v/v) sterile peat. Excellent results in suppressing at the same time Phytium ultimum damping-off on cucumber, Rhizoctonia solani damping-off on bean, Phytophthora nicotianae root rot on tomato, and Verticillium dahliae wilt on eggplant, reaching peaks of suppression up to 60%, were obtained using the two MSW-based composts amended with extracts recruited from the green composts. Some hypothesis about the most probable models involved in multi-suppressing diseases to understand the suppressive properties induced by the exogenous microbial consortia have been discussed in relation to different origin and composition of feedstock. The findings of this work suggest that the suitable use of ‘next-generation green compost’ as a profitable source of microbial consortia rather than as soil amendment seem be a useful opportunity to enhance the suppressive properties of composted MSW-based biomass with pathogen-specific property.