Evaluation of morphological damage caused by a low molecular weight chitosan on the fungus Bipolaris oryzae

Antimicrobial activity of chitosan has been previously demonstrated on some fungi species. In this work, the direct effect of a low molecular weight chitosan (121.6 kDa) on the morphology of Bipolaris oryzae was studied by light and scanning electron microscopy techniques. Changes in the hyphae and germ tubes were observed. Moreover, structural and morphological changes during the apical growth phase of the fungus were detected by scanning electron microscopy at 3 g/L chitosan. B. oryzae hyphae malformations were detected, with shortening and thickening of hyphae and spore germ tubes shortening and swelling, together with hyphae agglomerations, all these changes affecting the fungus' multiplication and spreading capacity. These results support the possible use of the assayed chitosan in pest control strategies against B. oryzae in rice crops.