In vitro evaluation of dew-retting of flax by fungi from southern Europe

Flax dew-retting is widely adopted in most flax-growing countries, but it d oes not represent a practical solution where dry weather conditions occur a fter harvest. A study of the local microbiological aspects was undertaken a s a contribution to improve field-retting of flax under southern European c limates. Fungi were isolated from soil and dew-retted flax in northern Ital y, and 23 representative strains were chosen to test their ability to ret f lax stems. Experiments were performed in vitro on flax stem pieces artifici ally inoculated with single fungal strains. Retting degree was assessed wit h a mechanical test, to evaluate the ease with which the bast was detached from the wood core, and by the analysis of the residual fibre pectins using uronic acid. Uronic acid dosage provided a better differentiation of the s trains than the mechanical test. There was a large variability in retting a bility among the species assayed and even among strains of the same species . The best results were obtained with all Aspergillus and Penicillium strai ns, while Mucor and Rhizopus strains showed a variable retting ability. Fus arium, Trichoderma strains and Epicoccum nigrum had the poorest retting abi lities among all the fungal strains assayed.