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Chemical structure of two phytotoxic exopolysaccharides produced by Phomopsis foeniculi
M M Corsaro1, C De Castro, A Evidente
1Dipartimento di Chimica Organica e Biologica, Università di Napoli Federico II, Napoli, Italy.
Abstract:
The two main exocellular polysaccharides produced in vitro by Phomopsis foeniculi, a fungal pathogen of fennel, were isolated and characterized by chemical and spectroscopic methods as a galactan with the known structure [-->6)-beta-D-Galf-(1-->5)-beta-D- Galf-(1-->5)-beta-D-Galf-(1-->]n and a mannan. The latter consists of a backbone of alpha-(1-->6)-linked mannopyranose units. Almost all of these are branched at the 2 position with arms containing 2- and 3-linked mannopyranose units. The crude polysaccharide fraction and its components, galactan and mannan, showed phytotoxic effects, i.e. chlorosis, necrosis and/or wilting, on fennel and on two non-host plants, tobacco and tomato.