Ultrastructural Aspects of Fusarium sulphureum and Alternaria alternate Affected by Extracts of Onion Peel

The effects of the extracts of onion peels on the growth, morphology, and ultrastructure of F. sulphureum and A. alternate were investigated. Antimicrobial activities of different concentrations (10, 20, 40, 80, 100, 120, 160, 200 mL/L) of OPEs were found. OPEs could inhibite the growth of F. sulphureum and A. alternate. With the rise of concentration of the extracts, the rates of the inhibition were also increased. Among all the different portion of extracts, RE was found to have the most inhibition ratio to F. sulphureum, up to 93.48% (200 mL/L). Morphology of the two fungi by light microscope showed that hyphae induced by OPEs presented morphological changes, including swelling, distortion and any other structure changes. Ultrastructural changes were observed in treated hyphae with twisting, collapse and shrink by SEM. This study suggests that the OPEs could impagine on the growth of mycelia of F. sulphureum and A. alternate.