BIOACTIVITY AND BIOCONTROL BY THE FUNGUS TRICHODERMA: A GREEN REVOLUTION FOR AGRO-RESIDUES

Large amount of agricultural wastes are produced every year and, among them, rice straw is one of the most abundant lignocellulosic crop residues in the world (1). Rice straw contains approximately 35-40% cellulose, 25-30% hemicellulose and 10-15% lignin. Native cellulose and lignin are highly resistant to enzymatic hydrolysis but fungal biological pretreatment, or biodegradation, serves as an attractive option that is both energy-saving and environmentally friendly (2, 3). Despite these agricultural residues contribute significantly to the waste disposal problem, their organic nature and nutrient content make them an interesting raw material that can be reintroduced in the agricultural sector as a fertilizer. An innovative approach consists in the use of these agro-waste residues for the development of “Bioactive Agro-matrices”, obtained by the integration of matrices derived from the agricultural and agri-food cycle (for example rice straw, corn cob, digestate,…) with viable microorganisms, opportunely selected, agronomically useful and safe for human health. The aim of the present work was to select microfungal strain/s able to grow on rice straw, to degrade it and, simultaneously, able to antagonize the phytopathogenic Fusarium spp., very harmful on rice crop. The work focused on Trichoderma spp., which are generally known as antagonists of several plant pathogenic fungi and as plant growth promoters. Their economic importance includes their roles as primary decomposers, producers of antibiotics and enzymes as well as biocontrol agents against a wide range of plant pathogens (4). In this study, the survival and growth ability of several Trichoderma isolates on rice straw were evaluated. Furthermore, their antagonistic behavior against different Fusarium strains were tested in vitro throughout plate assays. One of these, Trichoderma asperellum EVT4, was the most active towards Fusarium spp., in particular towards F. fujikuroi EVF3 and its antagonistic potential was also assessed in vivo (i.e. a microcosm test consisting of soil and rice straw). The fungal load of F. fujikuroi EVF3, expressed as CFU/gr, was significantly lower in the tests carried out in the presence of T. asperellum EVT4 compared to the control, in which this strain was alone. The load of T. asperellum EVT4, however, did not change significantly in the presence of F. fujikuroi EVF3. These first results indicated T. asperellum EVT4 as an interesting fungal strain, that can be added to rice straw in order to create a “Bioactive Agro-matrix” useful in field both for biological control of plant pathogens and for rice straw degradation.