Evaluation of the Bio-Stimulating Activity of Lake Algae Extracts on Edible Cacti Mammillaria prolifera and Mammillaria glassii

The research aimed to test different seaweed extracts derived from three macroalgae representatives, namely, Rhodophyta, Chlorophyta and Phaeophyceae, as a bio-fertiliser for the growth of Mammillaria prolifera and Mammillaria glassii and the production of edible fruits. The experiments started in September 2021 and were conducted in the greenhouses of CREA-OF in Pescia (PT). Three different algae, namely, Hypnea cornuta (Rhodophyta), Ulva ohnoi (Chlorophyta), collected from the brackish lake Ganzirri, in Messina, and Sargassum muticum (Phaeophyceae) from Venice lagoon, were tested. The experimental trial showed a significant improvement in the agronomic parameters analysed for the growth and production of cactus plants and fruits treated with the selected algae. A significant increase was found in the sugar, vitamin A, vitamin C and vitamin E content of the fruits of treated plants. In particular, the thesis with Ulva ohnoi was the best for plant growth and fruit production with a higher sugar and vitamin content. This experiment confirms the algae’s ability to stimulate soil microflora and microfauna, promoting nutrient uptake, participating in organic matter mineralisation processes and significantly influencing the nutraceutical compounds in the fruits.