Prospecting algae and cyanobacteria as bioprotectans for plant disease control

The European Directive 2009/128 on sustainable use of pesticides promotes the use of alternative approaches to synthetic products for plant disease control to reduce human, animals and environmental risks. Among alternatives, natural products based on cyanobacteria and algae are gaining attention. Our studies demonstrated that application of water extracts from Anabaena minutissima, Ecklonia maxima and Jania adhaerens controlled powdery mildew caused by Podosphaera xanthii on cucumber detached cotyledons and seedlings and induced the expression of PR genes related to plant-induced resistance. In addition, tomato seed treatment with the same extracts increased germination, seedling dry weight, calibre, and reduced root rot caused by Rhizoctonia solani on tomato plants. Seed treatment also increased chitinase activity and lignin compound contents in tomato seedlings. A deeper investigation on the possible bioactive compounds of A. minutissima, E. maxima and J. adhaerens, revealed the antifungal activity of polysaccharides against Botrytis cinerea, agent of grey mould, in vitro and in vivo on strawberry fruits. Latest research pointed out that application of phycobiliproteins from A. minutissima, Arthrospira platensis and Hydropuntia cornea on tomato fruits before B. cinerea challenge reduced grey mould disease. In particular, FT-IR and FT-Raman spectroscopies have shown that phycobiliproteins from A. minutissima preserved cutin and pectine structures of tomato fruit from B. cinerea infection. In conclusion, our research demonstrate the potentialities of algae and cyanobacteria as a bioprotectans for plant disease control.