Abstract
The antimicrobial activities of Xylopia aethiopica and Syzygium aromaticum extracts on fungi associated with rotting white and water yam was investigated. Diseased and healthy yam species of Dioscorea spp. were obtained from some markets. Fungal isolation was done from the samples using standard procedures. Leaves and fruits of X. aethiopica and S. aromaticum were obtained from the botanical garden, University of Ibadan, Ibadan. Crude aqueous and ethanol extracts of the plants were obtained using standard procedures. After pathogenicity tests, the isolated fungi were cultured on acidified potato dextrose agar (APDA) that were impregnated separately with the leaves and fruits of X. aethiopica and fruits of S. aromaticum extracts at specific concentrations for 10 days. Experimental design was completely randomized design (CRD) with three replicates. Mycelial extension of the fungi was measured daily using a meter rule. Data were subjected to statistical analysis using SAS software. Means separation was done using LSD (DMRT) at P≤0.05. The isolated fungi were identified as Aspergillus niger, Aspergillus fumigatus, and Penicillium chrysogenum. Pathogenicity test showed that the three fungi caused rotting in the yams. Growth inhibition of the fungi was significantly (P≤0.05) higher with ethanol extracts than aqueous extract. Highest mycelial growth inhibitory effect was recorded in the S. aromaticum fruit ethanol extracts on all the organisms. Likewise, X. aethiopica leaf aqueous extract showed high mycelial growth inhibition on A. fumigatus at 50 and 75% concentrations while X. aethiopica fruit ethanol and aqueous extracts was noted to have inhibitory effects on the growth of A. niger and P. chrysogenum at 50 and 75% concentrations respectively. The in vitro result underscores the antifungal abilities of these plant extracts and is also suggestive of their promising potential in vivo. Further works are underway to examine their antimicrobial potentials in the field. Key words: Dioscorea alata, Dioscorea rotundata, postharvest rot, Syzygium aromaticum, Xylopia Aethiopica.
Highlights
Yam belongs to Dioscorea family and is rated as one of the most important staple food crops in most parts of West Africa especially Nigeria (Olayemi and Ajaiyeoba, 2007)
The pathogenicity test conducted showed that A. niger, A. fumigatus and P. chrysogenum caused rotting on the water yam (Plate 4) and white yam (Plate 5) tubers in storage
The result showed that P. chrysogenum was more virulent on both yam tubers while the other fungi strains were not as virulent
Summary
Yam belongs to Dioscorea family and is rated as one of the most important staple food crops in most parts of West Africa especially Nigeria (Olayemi and Ajaiyeoba, 2007). Yams are root tuber bearing plants grown and harvested annually with over 600 species out of which, six are economically and socially important as regards export purposes, medicine and food (IITA, 2009). Plant Sci. Chinese yam, (Dioscorea esculenta), yellow yam (Dioscorea cayenensis) (Zaknayiba and Tanko, 2013; Lawal et al, 2014; Princewill-Ogbonna and Ibeji, 2015). The variation in taste of yam inspires it’s processing in different forms. Some yam tubers can be sliced and used as herbal medicine in China (Lee et al, 2003)
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