Combined Biostimulant Applications of Trichoderma spp. with Fatty Acid Mixtures Improve Biocontrol Activity, Horticultural Crop Yield and Nutritional Quality

The growing demand for safer foods reflects the public perception of the adverse consequences of chemicals used in agriculture. This research aimed at developing new biological formulations based on the combination of small microbial consortia containing two Trichoderma spp., with a medium–long chain fatty acids mixture (FAm). The bioactivity of these formulations was investigated on different vegetable crops in terms of biocontrol, growth promotion, yield and quality improvements. FAm application reduced Botrytis cinerea necrosis by up to 90% compared to the infected control plants and some of the assayed Trichoderma spp. + FAm combinations contained Rhizoctonia disease, reaching more than 90% reduction of tomato and lettuce plant mortality. An increasing yield, ranging to 25 and 90%, was recorded on treated tomato, lettuce and kohlrabi compared to untreated plants. A significant enrichment in carotenoids (+60%) and glucosinolates (+39%) was measured on biotreated plants compared to controls. Untargeted LC-MS analysis revealed a higher content of tomatine and dehydro-phytosphingosine, glycoalkaloids involved in defense responses, in Trichoderma spp. + FAm combination-treated plants. The combined biostimulant applications of Trichoderma spp. with FAm were able to improve the performances of different horticultural plant species, producing a premium quality marketable vegetable with higher antioxidant content.