Tomato seed biopriming with water extracts from Anabaena minutissima, Ecklonia maxima and Jania adhaerens as a new agro-ecological option against Rhizoctonia solani

In recent years, the use of synthetic pesticides in agriculture has been restricted for environmental pollution issues. Alternatives to chemicals for plant disease control are highly recommended by the recent EU legislation. We tested tomato seed treatment with water extracts from Anabaena minutissima, Ecklonia maxima, and Jania adhaerens for their biocontrol activity against the fungal plant pathogen Rhizoctonia solani. Algae were characterized into their contents in macro and microelements and into their functional groups by using FT-IR spectroscopy. The extracts were applied at 0.0, 2.5, 5.0, and 10.0 mg/mL concentrations on tomato seeds against the pathogen, in in vitro experiments and under greenhouse conditions. To estimate the efficiency of treatment in priming plant defence response, plant chitinase activity was measured and the different distribution of functional groups of roots was determined by FT-IR spectroscopy. Increases of germination and seedling dry weight for treated seeds without pathogen challenge were observed. The extracts reduced disease severity and increased seedling dry weight both in in vitro and greenhouse experiments at all concentrations. All extracts also increased stem seedling calibre under greenhouse conditions. The plant chitinase activity was increased by all extracts. The aromatic rings assigned to lignin changed with the treatment. We concluded that, although our experiments were based on a small scale, algae and cyanobacteria water extracts could provide a potential tool for the R. solani control on tomato plants, by contributing to the reduction of synthetic product input in the environment