Nurturing of Plantlets Using Cut Pieces from the Storage Roots of Sweet Potatoes(Ipomoea batatas(L.)Lam.)and their Productivity in the Field

Abstract

A new nurturing method was studied using pieces cut from storage roots to reduce the time-consuming and laborious works(raising, preparing, and transplating of cut sprouts), which accounts for about 60% of the total working hours in sweet potato production by the conventional method. The experiments were conducted in 1997 and 1998 using 1- and 10-g(fresh weight)cut pieces from storage roots(cultivar; Koganesengan). Five kinds of growth regulators were applied at the concentrations ranging from 0 to 200 mg L^-1 to promote rooting and shooting from the pieces. After the treatment with growth regulators, the pieces were subjected to an antiseptic curing treatment, and then incubated on wet vermiculite at 30°C. Rooting was effectively induced by IAA, and shooting by ABA, within one to two weeks. The plantlets were developed from 10-g pieces with periderm after the treatment with ABA, and were nurtured for 10, 30 and 50 days. They vigorously grew with no transplanting injury after being planted in the field in early May. They were harvested in late October and were compared for shoot growth and productivity with the control(the conventional method using cut sprouts). The plantlets nurtured for 50 days achieved the highest yield and the best qualities and did not show the thickening of mother roots obserbed in direct planting using whole storage roots. In conclusion, the new nurturing method is superior to conventional methods in both productivity and quality. However, there are still several problems to be solved, such as low shooting rate and so on.