John M. Ehiobu, Gideon I. Ogu, Phytochemical Content and In Vitro Antimycelial Efficacy of Colocasia esculenta (L), Manihot esculenta (Crantz) and Dioscorea rotundata (Poir) Leaf Extracts on Aspergillus niger and Botryodiplodia theobromae, JHPR Volume 1, Journal of Horticulture and Plant Research (Volume 1)
    The <i>In Vitro</i> efficacy of aqueous leaf extracts of common edible root crops (<i>Colocasia</i> <i>esculenta</i>, <i>Manihot</i> <i>esculenta</i> and <i>Dioscorea</i> <i>r</i><i>otundata</i>) were investigated against <i>Aspergillus</i> <i>niger</i> and <i>Botryodiplodia</i> <i>theobromae</i>. The fungi were isolated from rotten tubers of yam using antibiotic-amended potatoes dextrose agar. Graded aqueous leaf extract concentrations (25 g/L, 50 g/L and 75 g/L) of each plant were applied against each test fungi on PDA plates and their mycelial growth inhibition activities were monitored for 144 hrs. Camazeb (5 – 10 g/L), a fungicide, was used as positive control agent. The phytochemical constituents of each extracts were also analyzed using standard techniques. The patterns of antifungal activities of the extracts were concentration and pathogen dependent. The most effective mean mycelial growth inhibitions were found with <i>D. </i><i>esculenta</i> and <i>C. </i><i>esculenta</i> against <i>B. </i><i>theobromae</i> (61.9 – 80.9 %) and <i>A. </i><i>niger</i> (63.8 – 82.8 %), respectively. Though, <i>M. </i><i>esculenta</i> leaf extracts generally demonstrated the least antifungal activities against both pathogens, their activities were significant at 75 g/L. The antifungal potency of both <i>D. </i><i>esculenta</i> and <i>C. </i><i>esculenta</i> were comparable to Camabez (chemical fungicide), which demonstrated 100 % inhibition at both 5 and 10 g/L concentrations. Higher concentrations of saponins (5.64 - 6.71 mg/100g), tannins (4.42 – 7.23 mg/100g) and flavonoids (3.64 – 5.25 mg/100g) were detected in the extracts, and could probably be linked to the observed antifungal activities. Findings from this study showed that <i>D. </i><i>esculenta</i>, <i>C. </i><i>esculenta</i> and <i>M. </i><i>esculenta</i> posses bioactive molecules that could be exploited in the bio-control of phyto-pathogens of tubers crops, which are the main staple food in most tropical countries.
    Antimycelial Efficacy, Phytopathogens, Potato Dextrose Agar, Tuber Crops