Non-Destructive Assessment of Leaf Chlorophyll and Epidermal Flavonoids in Two Tomato Cultivars (Solanum lycopersicum L.) Grown Under Different Trichoderma Spp. Treatments

Summary The purpose of this study is to examine the effects of different Trichoderma spp. treatments (T1: Trichoderma harzianum, T2: Trichoderma brevicompactum, and T3: T1 + T2) on two tomato cultivars (‘Narvik’ and ‘Gružanski zlatni’) by the non-destructive monitoring of chlorophyll (Chl) and epidermal flavonol (Flav) indices and nitrogen balance index (NBI) in their leaves. The main objectives were to compare the responses of tomato cultivars considered (grown in a greenhouse) to different Trichoderma strains and a combination of Trichoderma strains. Variations in the Chl, Flav, and NBI values obtained were significantly influenced by nearly all the factors examined (namely the tomato cultivar, experimental week, and treatment), the interaction of which was found significant for all the parameters analyzed. The results obtained indicate that the combinations of strains in the T3 treatment markedly enhanced the Chl content in the ‘Narvik’ cultivar in some experimental weeks. Moreover, reduced NBI values were determined in the Trichoderma-treated ‘Narvik’ plants due to the increased flavonol content, which indicates a shift from primary to secondary metabolism. Further research, including the same cultivars and treatments, is warranted under field conditions to evaluate the physiological responses of the ‘Narvik’ and ‘Gružanski zlatni’ tomato cultivars in a multiple-stressor environment.