Seed Coating with Trichoderma harzianum T-22 of Italian Durum Wheat Increases Protection against Fusarium culmorum-Induced Crown Rot

Changes in root organization and colonization could be relevant for wheat’s (Triticum durum Desf.) response to F. culmorum-induced crown rot disease (FCR). We investigated the biocontrol and biostimulant efficiency of seeds coated with T. harzianum T-22 (T-22) of four tetraploid wheat seedlings (ancient Saragolle Lucana and modern Creso, Simeto, and Ciclope). In an in vitro experiment, T-22 repressed F. culmorum mycelium growth by over 50% due to the probable combination of competition for nutrients, mycoparasitism, and antibiosis. The seed germination rate was not significantly affected by T-22 while the F. culmorum-induced decrease in emergence was attenuated in the presence of T-22. Ultimately, an improvement in growth was observed by comparing treated and control seedlings at 21 days after sowing. Inoculation with T-22 resulted in Saragolle Lucana seedlings being 4.69 cm higher while Ciclope and Simeto had main roots that were 9.96 and 8.13 cm longer than the control, respectively. Treated and infected Simeto seedlings were 3.75 cm higher and had roots that were 14.45 cm longer than the control, with little contemporary dense coiling colonization by T-22, like Saragolle Lucana. Seed coating induced the best performance regarding seedling growth and the ability to control the pathogen in Simeto (disease severity reduction rate (DDR) of 20%). The pathogenicity of F. culmorum was reduced in all four durum wheats, although it was highly susceptible to FCR. Ciclope, studied for the first time, showed a decrease in disease incidence from 100 0.00% to 56.67 9.13% and a 30% DDR. The seed coating influenced the seedlings’ response to FCR due to T-22’s different colonization actions. This study provides new explanations for the diverse responses of ancient and modern tetraploid wheat to F. culmorum mediated by T-22 inoculation via seed coating.