Newly isolated Trichoderma spp. show multifaceted biocontrol strategies to inhibit potato late blight causal agent Phytophthora infestans both in vitro and in planta

Abstract

Potato growers worldwide are embattled in a war since more than 150-years with an enemy whose lifecycle, genome size and architecture, and economic impacts are the epitome of a plant pathogen. Phytophthora infestans (Mont.) de Bary is an oomycete that causes the notorious late blight infection in potato and tomato. In this study we explored the benefits of the multi-talented plant symbiotic fungi Trichoderma spp. and of their metabolites as potential biopesticides against P. infestans. Eleven strains of Trichoderma spp. were obtained from soil and tree barks and were identified using DNA sequence analysis. The antagonistic potential of the strains against P. infestans was first evaluated in vitro. In dual culture assays, P. infestans growth was significantly inhibited (53-95%) by different Trichoderma spp. through direct mycoparasitism, competition for space and nutrients, and/or antibiosis. The cell-free filtrates (CFF) of different Trichoderma strains were obtained, characterized for anti-Phytophthora activities as well as biochemical stability. The results indicated that Trichoderma CFF were chemically stable and strongly decreased P. infestans’ mycelial growth as well as zoospore motility and viability. Similarly, Trichoderma CFF showed significant protection against P. infestans infection in leaf disk assays. Ultra-performance liquid chromatography analysis revealed the presence of harzianic (HA), iso harzianic (iso-HA) acid and 6-Pentyl-2H-pyran-2-one (6PP) as major compounds in different Trichoderma CFF. Furthermore, selected Trichoderma strains significantly protected potato plants against soil-mediated late blight infection. Finally, Trichoderma spp. showed high compatibility with a copper-based fungicide, suggesting that both protective agents could be combined in integrated pest management program.