Control of some Penicillium and Aspergillus rots of Discorea alata Poir and Discorea rotundata L. using extracts of Xylopia aethiopica (Dunal.) Linn. and Syzygium aromaticum (Linn.) Merr.

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.