Pythium aphanidermatum pathogenicity to hydroponics lettuce and its biocontrol with Trichoderma

Abstract

The objective of this work was to evaluate the pathogenicity of Pythium aphanidermatum to lettuce varieties, and the action of the product Biotrich, formulated with Trichoderma, in the control of this pathogen and its effect on plant growth promotion. In a in vitro experiment, germinated seedlings of Vera and Elisa lettuce varieties were placed in Petri dishes with water-agar and 1mL Biotrich suspension (0.2 mL L^-1), and after 24 hours, on plugs with the Pythium isolate mycelium. The evaluations were done ten days after the incubation at 20 and 31ºC. In vivo experiments were carried out during the spring and summer, using the Nutrient Film Technique (NFT) system, in a completely randomized design, following a 2x2x2 factorial arrangement, as well: two varieties; pathogen abscence or presence; and with or without Biotrich addition. At the end of cultivation, the fresh and dry weight of shoots and roots were analyzed. In vitro, P. aphanidermatum had increased aggressiveness at 31ºC. However, no pathogenicity was observed in vivo. Generally, Biotrich did not promote plant growth; however, it was effective in controlling the pathogen in vitro. Pythium aphanidermatum is pathogenic to lettuce varieties Vera and Elisa, at 20 and 31°C, and Biotrich is effective for its control at these temperatures.