DRY SEASON CONSERVATION AND MULTIPLICATION OF SWEET POTATO [IPOMOEA BATATAS (L) LAM.] PLANTING MATERIAL IN THE COASTAL SAVANNAH ZONE OF GHANA

ABSTRACT

Three experiments were conducted during the dry season from October 2001 to April 2002 at the University of Ghana Farms and the Food Research Institute, to evaluate two methods of conservation of sweet potato planting material and one method of multiplication of vines were evaluated in this study using two cultivars - Sauti and Okumkom released to farmers by the Crops Research Institute. The study was aimed at developing a technology to ensure the availability of adequate quantities of sweet potatomplanting material at the beginning of the planting season. In Experiment 1, small unmarketable tubers were stored in an improved bam for 0, 5, 10 and 15 weeks and then planted in the nursery. Sprouts from tubers planted were used to generate planting material for field planting of sweet potatoes. In Experiment 2, small unmarketable tubers of two sweet potato cultivars, Sauti and Okumkom, were planted at three different planting distances; 25cm x 10cm, 25cm x 15cm and 25cm x 20cm and evaluated for their vine yields. In Experiment 3 the effect of the conservation of vines of Sauti and Okumkom in the nursery and early initiation of vine multiplication were evaluated. Except for sweet potato weevil (Cylas puncticollis (Sum) ) damage in tubers in which significant differences (P=0.05) were observed between the cultivars, results obtained from storage of tubers showed that differences between the cultivars were not significant for percentage weight loss, percentage shriveling, percentage sprouting and percentage rotting. However, for the different periods of storage, the percentage weight loss, percentage shriveling, percentage rotting, percentage insect damage and percentage sprouting increased significantly with increased period of storage. The resultant number of 30 cm apical, middle basal and total number of 30cm vines obtained from the remaining tubers planted, decreased significantly with increase in storage period. Although differences observed among the different planting distances studied were not significant at P=0.05, planting both cultivars at 25cm x 15cm gave the highest number of planting material followed by 25cm x 10cm and then 25cm x 20cm Early initiation o f multiplication of planting material after conservation of vines in the field - 14 weeks before field planting, gave the highest number of 30 cm apical, middle, basal and total vines available for field planting, followed by 10, 8, 6, 4, and 0 weeks in decreasing order. Differences observed were significant at P=0.05.