Exploring the impact of Verticillium wilt disease on the mechanical properties of elementary flax (Linum usitatissimum L.) fibres

Abstract : Verticillium wilt is a disease caused by the fungus Verticillium dahliae (V. dahliae) which is widespread in flax (Linum usitatissimum L.) cultures. V. dahliae negatively impacts the fibre yield with up to 60% loss at the scutching step of fibre transformation. Yet, little is known about the consequences of V. dahliae on the mechanical properties of flax fibres. In this study, we investigated the tensile characterisation of elementary flax fibres impacted by V. dahlia. Using elementary tensile tests, we observed an important decrease in the mechanical properties of the studied flax fibres, with a 32% decrease of the tensile strength at break and a 15% decrease of the strain at break. Further investigation of the flax fibres cell wall using atomic force microscopy (AFM) in peak-force non-quantitative mechanical mapping mode, showed a 23% decrease in the longitudinal indentation modulus of flax fibre cell walls, measured directly in their cross section. This is arguably due to the important enzymatic arsenal of V. dahliae revealed by a bioinformatic analysis of secreted carbohydrate-active enzymes targeting plant cell wall components. The coupling of this analysis with electron microscopy observations and sugar analysis highlighted the degradation mechanisms of this fungus which significantly affects the mechanical performance of flax fibres