Antifungal effects of two botanical extracts and honey on fungi associated with sunflower (Helianthus annuus L.) seeds

Abstract

The antifungal efficacy of Phyllanthus amarus and Trianthema portulacastrum ethanolic leaf extracts, and honey were investigated in-vitro against fungi of sunflower; Helianthus annuus L. seeds. The study tested four varieties of sunflower seeds namely SAMSUN 1, SAMSUN 2, SAMSUN 3 and SAMSUN 4. The culture and isolation of the seed-borne fungi were carried out using the Agar Plate method while the inhibitory assessment was done by using the agar well diffusion method. Fungi identification was done through observation of colony appearance and microscopic evaluation. Ethanol extract of the leaf sample was obtained, filtered, and evaporated at 65 °C under a reduced pressure. The result showed that Aspergillus, Penicillium and Fusarium genera were isolated from the seeds. The honey treatment produced the highest inhibition response of 9.3% (4.2mm) and 8.0% (3.6mm) against Penicillium spp and Aspergillus niger respectively. This was followed by the honey combination with ethanolic leaf extract of T. portulacastrum and the combination with ethanolic leaf extract of T. portulacastrum which both inhibited Penicillium spp. at 7.1% (3.2 mm). The extract of P. amarus recorded the least inhibition of the radial growth at 3.8% (1.7 mm), 3.3% (1.5 mm) and 2.6% (1.2 mm) against A. niger, F. oxysporum and A. flavus respectively. At five days after inoculation (DAI). From this study, honey only or when combined with T. portulacastrum ethanolic leaf extract could serve as promising agents for producing seed dressing botanical fungicides.