No abstract

The annual vegetative cycle of the yam (Dioscorea spp) necessitates a long period of storage. Losses during this period are high and are mainly due to germination. Trials on the effectiveness of gibberellic acid (GA3) for controlling storage losses were carried out on the two main species of yam (D cayenensis rotundata and D alata) grown in the Ivory Coast. Methods of application at the apex adapted to the rural environment were tested. Treatment with GA3 prolonged the dormancy period and thus reduced losses. This substance was effective at low concentration with a long soaking duration (75 mg litre−1 for 2 h) and during a soaking of short duration with a higher concentration (0·5 h at 150 mg litre−1). Because of its stability at ambient temperature, the solution was still active 3 days after being prepared and after reuse of the same dip six times. © 1998 SCI.

Two aspects of yam storage practice were tested from 1994 to 1995 in central Côte d'Ivoire. The first experiment compared the storage environment in pits or sheds with that of the traditional yam open barn method. The pits allowed the daily range of variation in temperature to be reduced while maintaining a high relative humidity (RH), whereas the temperature and RH in the sheds were similar to those of the yam barns. Differences in temperature and RH between the storage systems had little effect on the fresh weight losses of the tubers. The more effective protection against solar radiation and rain afforded by the sheds and pits reduced fresh weight losses in D. cayenensis rotundata by 12% over 6·5 months in comparison with the barns. The second experiment tested the regular removal of the sprouts. Sprout removal reduced fresh weight losses equally over 5 and 6 months' storage. The reduction in fresh weight loss was 12% for cv. Gnan (D. cayenensis rotundata) during 6 months' storage. Monthly sprout removal gave an equal benefit in pits, in sheds and on yam barns. The monthly cutting of sprouts at the base should be encouraged in places where this is not already done. The total loss is mainly determined by the growth of the sprouts and the reduction in weight after onset of sprouting, which are highly dependent on species and cultivar. Bètè bètè yams had better keeping qualities than all the other cultivars tested.