In vitro antagonism of Trichoderma against Sclerotium rolfsii from potato (Solanum tuberosum)

Background/Objective. Trichoderma constitutes a viable alternative for reducing the destructive potential of soft rot (Sclerotium rolfsii) in potato crops. The objectives of this research were to determine the in vitro antagonistic effectiveness of Trichoderma asperellum, T. asperelloides, T. afroharzianum, and T. azevedoi against S. rolfsii (Scr4 and Scr17) and to determine the hyphal interactions of the antagonists, on addition to determinate the inhibition of mycelial growth of S. rolfsii (Scr4) by volatile metabolites produced by Trichoderma species. Materials and Methods. The in vitro biological effectiveness of 16 T. asperellum isolates, five T. asperelloides isolates, four T. afroharzianum isolates, and one T. azevedoi isolate in inhibiting S. rolfsii (Scr4 and Scr17) mycelial growth was studied. The type of hyphal interaction between the same Trichoderma spp. isolates and S. rolfsii (Scr4) was also determined. The effect of volatile metabolites produced by Trichoderma spp. isolates on the inhibition of mycelial growth of S. rolfsii (Scr4) was evaluated. Data on mycelial growth inhibition were analyzed using nonparametric statistical analysis (Kruskal-Wallis), and the mean separation was performed using the procedures of Conover (1999) with (P ≤ 0.05). Results. In dual confrontations, Trichoderma species showed mycelial growth inhibitions of 21.0 to 75.4% and 23.6 to 77.1% in S. rolfsii isolates Scr4 and Scr17, respectively. Hyphal interactions of the same Trichoderma species consisted of vacuolization, granulation, coiling, adhesion, lysis, and penetration into the pathogen (Scr4); all four Trichoderma species inhibited mycelial growth (26.0 to 81.4%) of S. rolfsii. T. azevedoi stood out among the isolates for showing greater antagonistic capacity in all tests. Conclusion. The results indicate that Trichoderma species, especially T. azevedoi (TAI73), inhibited the growth of S. rolfsii Scr4 (75.4%) and Scr17 (77.1%). T. azevedoi (TAI73) caused vacuolization, granulation, coiling, adhesion, and lysis of hyphae in the Scr4 isolate.