Effect of Trichoderma on Growth and Sporangia Production of Phytophthora capsici

Phytophthora capsici is the main agent of chili pepper root rot, causing significant yield losses in commercial fields worldwide. Management of this plant pathogen has been difficult due to its ability to develop fungicide resistance, therefore biocontrol of P. capsici appears to be a promising alternative. In this study we evaluated the effects of three species of Trichoderma: T. harzianum (Th-7), T. koningiopsis (Tk NRRL50190) and T. asperellum (Ta NRRL50191) on two mexican isolates of P. capsici (RDP-1 and RDP-2) obtained from commercial pepper fields in Aguascalientes, Mexico. The ability to inhibit mycelia growth of P. capsici was tested with in vitro assays, followed by the quantification of sporangia after dual confrontations. All Trichoderma isolates inhibited the mycelia growth of the phytopathogen, but only Ta and Tk showed mycoparasitism. Sporangia production of P. capsici RDP-1 and RDP-2 was significantly reduced by Trichoderma isolates, compared to the non-confronted control, except for the Th-RDP-2 confrontation. Sporangia of RDP-1 significantly decreased by 95.6%, 81.3% and 78% after confrontations with Tk, Ta and Th, respectively; and by 76% and 85.4% in RDP-2 by Tk and Ta, respectively. The results suggest that Ta, Tk and Th could be used as potential biocontrol agents of Phytopthora root rot, however, further studies are necessary to test the in vivo protection of Ta, Tk and Th and their synergistic effects against Phytophthora root rot of chile peppers and other P. capsici susceptible solanaceous and cucurbitaceous crops such as tomatoes, squash, melons, and cucumbers.