Abstract
The antifungal activity of the ethanolic crude leaf extracts of Dioseoreadumetorum and Psidium quajava on the fungal pathogens isolated from infected onion bulbs were investigated in vitro and in vivo. The pathogens were Aspergillus niger and Rhizopus stolonifer. For the in vitro antifungal assay, various concentrations of the extracts ranging from 10g/200ml, 20g/200ml, 30g/200ml, 40g/200ml and 50g/200ml were separately added to PDA media. The fungal pathogens were separately inoculated into the media and incubated for seven days. For the in vivo assay, healthy onion bulbs were properly surface sterilized using 99% ethanol and sodium hypochlorite (bleach). The sterile onion bulbs were then sprayed with the extracts at different concentrations two hours prior to inoculation with the fungal pathogens. Each onion bulb after being treated with different concentration of the extracts of 10g/200ml, 20g/200ml, 30g/200ml, 40g/200ml and 50g/200ml were dipped into beakers containing dissolved spore of each pathogen and incubated for seven days. Results of the in vitro antifungal assay shows that at 10g/200ml – 50g/200ml concentration, ethanolic leaf extracts of D. dumetorum and P. guajava completely inhibited the radial growth of A. niger and R. stolonifer after seven days observation period. For the in vivo antifungal assay, results shows that the extracts had a significant effect (P<0.05) on the mycelial growth of the fungal pathogens at all the different concentrations tested. Pathogen growth inhibition was most effective at 30g/200ml, 40g/200ml and 50g/200ml concentrations. The inhibitory action of the extracts increased/decreased with a corresponding increase/decrease in the concentration of the plant extracts. Ethanolic extracts of D. dumetorum was found to be more effective in inhibiting the growth of the fungal pathogens than P. guajava extracts.
Highlights
The onion (Allium cepa L.), known as bulb (Fritsch and Friesen, 2002), or common onion, is one of the most widely cultivated species of the genus Allium
The results of this study revealed that the fungi were responsible for the post harvest rot of onion bulbs in Calabar Metropolis as evidenced by the pathogenicity tests
The results showed that, the extracts significantly (P
Summary
The onion (Allium cepa L.), known as bulb (Fritsch and Friesen, 2002), or common onion, is one of the most widely cultivated species of the genus Allium. The species is probably native to South-western Asia but is commercially grown throughout the world, in the temperate zones (Ozer and Koycu, 2004). Due to its enormous commercial and medicinal value, the plant is cultivated in almost all countries of the world and consumed across the globe (Rai and Yadar, 2006). Onion belongs to the Lily family, Alliaceae, some classification place it in the family Liliaceae (Fritsch and Friesen, 2002). The species is biennial but usually grown as annuals in the temperate climates.
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