Tetradesmus obliquus extracts as bio-inputs for vegetable crops

Abstract

The objective of this project was to obtain Tetradesmus obliquus extracts, evaluate their fungicidal and bactericidal activity and assess their biostimulant effect on lettuce (Lactuca sativa) and tomato (Solanum lycopersicum) seedlings. After culture, 7 extracts of microalga were obtained to assess their biopesticidal activity in vitro. The studied phytopathogens of agricultural importance were Clavibacter michiganensis, Ralstonia solanacearum, Alternaria sp. and Fusarium oxysporum. The results showed that the most diluted extract, prepared from freeze-dried microalgal biomass resuspended in water, exhibited antibacterial activity against C. michiganensis and R. solanacearum, as well as antifungal activity against Alternaria sp. The biostimulant effect of the extracts on the growth of lettuce and tomato plants was evaluated. Extracts prepared from the microalgal culture and from freeze-dried biomass resuspended in water promoted rapid cotyledon emergence (Lettuce = 3 days and Tomato = 7 days), increased the production of seedlings with higher dry matter content (Lettuce = 76.8% and Tomato = 21.2%), thereby promoting a balance between the aboveground and root systems and improving seedling quality. In conclusion, T. obliquus extracts showed great potential as multifunctional bio-inputs, with biopesticidal and biostimulant activity in lettuce and tomato.