Control of Posthavest Rot of Sweeetpotato (Ipomoea batatas Lam.) Tuber in Vitro and in Vivo

Abstract: A laboratory experiment was conducted at Michael Okpara University of Agriculture Umudike, to determine the inhibition potentials of some indigenous medicinal plants and their essential oils against some plant pathogens associated with sweet potato soft rot in vitro and in vivo. The essential oils were extracted from five indigenous medicinal plants; A. indica (seeds), Z. officinale (rhizome), C. citratus, C. sineensis (peels) and O. gratissimum (leaves) and four   species were isolated from diseased tubers, Erwinia, Flavobacteria, Ralstonia, and Bacillus and later subjected to pathogenicity tests based on their respective ability to cause rot in healthy sweet potato tubers. The experiment was replicated four times using Completely Randomized Design (CRD). Erwinia, Ralstonia and Flavobacteria were positive as pathogens, while Bacillus spp was discarded as a non pathogenic organism on potato tuber. Data obtained showed that in the in vitro trials, all the extract and oils assayed inhibited growth of the pathogens in culture to varying degree when compared with that of the control (sterile water). Z. officinale oil was however found to be most effective in the inhibition of Erwinia pathogen with diameter of 19.33 mm while the control had the least (0.00 mm). In the in vivo experiment, C. citratus and A. indica performed much better than oil extracts of the rest and sterile water (P≥0.05). It was therefore concluded that there was a variation in the potency of the extract oils as well as in the sensitivity pattern of the test organisms. The potentials of the plant essential oils to serve as possible bio-control and antimicrobial agents for bacterial soft rot of sweet potato were thus demonstrated in this trial.