Peat, mainly imported from the northern and eastern European regions, is the basic component of growing substrates commonly utilized for cultivation of plants of horticultural and ornamental interest, both in pots and in benches. Peat is used as it is in some crops, but, in most cases, it is employed in mixture with other components. Due to its features, such as homogeneity, high water absorption capacity, good aeration, structural stability, a limited nutrient content and pH value, sphagnum peat represents the starting material most frequently used for substrates production. During the past few years, the supply of peat is hampered by environmental and economical constraints. Recently, the European Commission decided to exclude all substrates containing peat from the release of the Community Eco-Label Mark. In this respect the need to reduce peat in ornamental substrates drew great attention and resulted in increasing research activity to set up new and innovative substrates for horticultural and ornamental plants market. The aim of the present work is to give an overview of the possible application of beneficial microorganisms, particularly fungi belonging to Trichoderma genus, as growing media inoculants in order to develop innovative, economical and suitable substrates alternative to peat for cultivation of species of ornamental interest. The genus Trichoderma consists of anamorphic fungi isolated primarily from soil and decomposing organic matter, with teleomorphs, when known, belonging to the ascomycetous genus Hypocrea (order Hypocreales). Their lifestyle is generally saprotrophic with minimal nutritional requirements; they are able to grow rapidly on many substrates, can produce metabolites with demonstrable antibiotic activity and may be mycoparasitic against a wide range of fungal pathogens. They are involved in fundamental activities that ensure the stability and productivity of both agricultural and natural ecosystems. Recent discoveries show them as opportunistic, avirulent plant parasites, able to form mutualistic relationships with plants. Some Trichoderma strains, described as rhizosphere competent and commercially developed, can cause asymptomatic infection of roots, where the fungus colonization is limited to the outer cortical regions. This intimate interaction with the plant provides a number of benefits only recently recognized for their variety and importance, including: increased resistance of the plant to biotic stresses through induced or acquired systemic resistance and to abiotic stresses such as water deficit/excess, high salinity and extreme temperature; enhanced nitrogen use efficiency by improved mechanisms of nitrogen reduction and assimilation, reduced overexpression of stress genes and accumulation of compounds toxic to plant pathogens during plant response.
Keywords: Endophytism, Camellia, Limonium, Cupressus, biocontrol