ROOT QUALITY OF FOUR SWEETPOTATO [Ipomoea batatas (L) Lam] CULTIVARS AS AFFECTED BY DAYS AFTER PLANTING

Abstract

Time to harvest sweet potato is paramount in determining the yield and nutritional composition. Establishing an appropriate period to harvest non-white fleshed sweet potato [Ipomoea batatas (L) Lam] cultivars introduced in Ghana as food crops is relevant to their promotion for human health. However, there is insufficient scientific information on the root quality (root yield, fresh foliage weight, (3-carotene, dry matter, starch, fructose, glucose, sucrose, zinc, iron and protein) of these orange and purple-fleshed sweet potato cultivars as affected by days after planting (DAP), hence this study. Four cultivars, orange-fleshed (TUO) and purple-fleshed (TUP) were the newly the introduced ones from the Tuskegee University. Apomuden (APD), a released orange-fleshed in Ghana and Voggu (VOG) a landrace were used to investigate the effect of DAP: 65, 95, 125 and 155 on the root quality. Randomized complete block design was used. Nutrients were determined using Near-Infrared Reflectance Spectroscopy in Kumasi while, root yield and fresh foliage weight were quantified gravimetrically. The highest root yield was 28.20 t/ha observed at 125 DAP and the least was 6.30 t/ha observed at 65 DAP. Among the cultivars, APD gave the highest root yield of 19.50 t/ha, VOG had the lowest root yield of 15.80 t/ha. Fresh foliage weight was 30.40 t/ha high at 125 DAP and the least was 6.44 t/ha at 155 DAP,, The highest 13-carotene content was 18.50 mg/100 g observed at 155 and the least was 12.60 mg/100 g obtained at 65 DAP. Among the cultivars, it was only the OFSP cultivars that contained I3-carotene content, the pattern was APD > TUO > VOG. TUP was. devoid of 13-carotene, it was rather the highest cultivar in dry matter and starch. Starch and dry matter contents were high at 95 and 125 DAP respectively. They were both low at 155 DAP. Fructose and glucose declined from 65 to 155 DAP but sucrose was rather the reverse. Once 125 DAP recorded the highest root yield and had good 13-carotene content, it is concluded that 125 DAP is the appropriate time to harvest these cultivars for maximum root quality.