In vitro Inhibition of Fusarium by Lactic Acid Bacteria (LAB): Implication of Yam Disease Control for Economic Growth in Nigeria

Yam is an important crop in Nigeria, where it is produced both as food and cash crop. Fusarium rots
of yam are among the most important postharvest pathogens of yam worldwide, causing a lot of
postharvest losses in stored yam tubers. Lactic acid bacteria (LAB) lower the pH and create an
environment that is unfavorable to pathogens and spoilage organisms. In vitro inhibition of fusarium
species by LAB was investigated; mono-culture and multi-cultures were used. The inhibition tests
were carried out with pure cultures of LAB and fusarium spp. The pure culture of actively growing
Fusarium was inoculated into Potato Dextrose Agar medium aseptically and then incubated at room
temperature for 72 h. The diameter of the growing Fusarium was measured, after which less than a
loop full of actively growing (18-24 h) LAB isolates were used to inoculate the medium containing the
growing Fusarium at a known distance in the same plate. The whole set up was incubated at 300C
and inhibition zones on Fusarium by the LAB were observed 24 hourly for 96 h. The tests were
carried out for mono-culture and multi-cultures in triplicate. The inhibition zone ranged from 43 to
100% in mono-culture plates and from 40 to 113% in multi-culture plates. The slightly larger inhibition
in the multi-culture plate may be due to much pressure on the Fusarium. Hence LAB may be used to
control rot caused by Fusarium in in stored yam, which can improve yam tuber storage for better
economic growth.