Biological control of Pythium aphanidermatum root rot and growth promotion of hydroponic lettuce by Clonostachys rosea

Biological control of Pythium aphanidermatum root rot and growth promotion of hydroponic lettuce by Clonostachys rosea Clonostachys rosea was evaluated for growth promotion and control of root rot (Pythium aphanidermatum) in hydroponic lettuce in NFT and floating systems. For growth promotion, Clonostachys (0, 10(3), 10(4), 10(5), 10(6) and 10(7) conidia/mL) was added in nutrient solution (NS) and the mass of the plants was measured. To evaluate the control of the disease in NFT, Clonostachys was applied to the NS (10(6) conidia/mL) i. one day after transplanting in the absence of Pythium; ii. three days before and simultaneously with Pythium infestation; and, iii. three days before, simultaneously and three days after Pythium infestation. To evaluate the control of root rot in floating system, Clonostachys was added in NS (106 conidia/mL) i. four days before, and at the moment of pathogen infestation, and, ii. four days before, simultaneously, and four days after pathogen infestation. Plant mass and the recovery of pathogen and antagonist from the roots were evaluated. Clonostachys did not improve plant growth in the absence of Pythium. In the NFT system Clonostachys protected the plants from yield losses caused by Pythium, but not in the floating system. Pythium recovery from the roots was reduced by 28,6% and 42,8% when Clonostachys was applied two or three times, respectively.