Effect of algae extracts of Sargassum genus on the germination and growth of lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.)

Algae are a rich source of bioactive compounds with diverse biological properties, such as biofertilizers. The research of such bioactive compounds potentially usable in agriculture represents a way of valuing this resource. The Morocco coasts, in particular the coast of El Jadida is known for its abundant diversity of marine macroalguae. This study aims to evaluate the biofertilizer potential of Sargassum muticum and Sargassum vulgare extracts on germination and seedling of lettuce (Lactuca saliva L.) and radish (Raphanus sativus L.) using different concentrations (0.5; 2.5 and 5 mg ml). In vitro tests shows that the algae studied exhibit biofertilizing properties. The observed effects vary according to the algae, the concentration tested and the target species studied. In terms of germination, the addition of crude extract from Sargassum muticum or Sargassum vulgare to the culture medium at low concentration does not have any effect on lettuce and radish seeds. At high concentrations (5 mg ml⁻¹), Sargassum muticum extract inhibited lettuce germination by 72.08%, while Sargassum vulgare caused 12.89% inhibition in radish. For radish, the Sargassum vulgare extract at high concentration causes an inhibition of 10.61%. Regarding seedling growth, the presence of crude extract from Sargassum muticum at 0.5 mg ml⁻¹ results in a significant increase in root elongation in lettuce (25.43%) and inhibition in radish (9.36%). The extracts from both sargassum species induce an increase in biomass production in both lettuce and radish.