The goal of this study was to evaluate quality changes during deep fat frying of five cultivars of sweet potato (Ipomoea batatas L.

The sweet potato (Ipomoea batatas (L.) Lam.) requires a long, hot growing season to attain good yields. In a cool climate, the use of black plastic mulch to heat the soil can improve growth but cultivars, plant spacing, and harvest date must be carefully selected to optimize yields and to attain market quality standards. In this two-year study in Quebec, Canada, two sweet potato cultivars ('Georgia Jet' and 'Beauregard') were grown at four in-row spacings (15, 30, 45, and 60 cm) and harvested at three dates (mid September, late September, and early October). Cumulative growing degree-days (GDD) with base temperatures of 10°C and 15.5°C were calculated for each harvest date. 'Georgia Jet' had higher total and marketable yields than 'Beauregard'. In-row spacing had no effect on yields per hectare of 'Beauregard' and only affected 'Georgia Jet' in one year of the study. Average root weight of sweet potatoes, yields per plant, and number of roots per plant increased with wider spacing. Delaying harvest by one or two weeks had little effect on 'Beauregard' but increased yields of 'Georgia Jet'. GDD may be a useful predictor of optimum harvest date but a lower base temperature used to calculate GDD may be desirable with 'Georgia Jet' as its yields continued to increase even when growing under cool conditions of late September and early October.Key words: sweet potato, Ipomoea batatas, mulch, spacing, harvest date, degree-days.

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There is an increased interest in producing sweetpotato (Ipomoea batatas) in parts of eastern Canada, which are farther north and have fewer growing degree days (GDD) than traditional production regions in the southern United States. There is currently little information on cultivar selection for farmers in these northern regions. We evaluated yields and quality of 15 sweetpotato cultivars and selected lines grown with black plastic mulch but without pesticides. The best marketable yields (18–25 t·ha−1) in this trial were comparable to average marketable yields obtained in traditional sweetpotato-producing regions. Of the orange-fleshed cultivars and selected lines, Beauregard, B94-24, and Evangeline had high yields and warrant further testing. Covington, a common cultivar in North Carolina and Ontario, had poor yields in our conditions: it may require more GDD. ‘Porto Rico’ and ‘Ginseng Red’ had poor yields mainly because their storage roots were too small. The yellow-fleshed ‘Georgia Jet’ and GJ2010 had very vigorous vines and produced high yields, but had a high culling rate because of malformed or cracked storage roots. The white-fleshed ‘Murasaki-29’, ‘O’Henry’, and ‘Japanese’ also had high yields; whereas ‘White Travis’ and ‘Korean Purple’ had poor yields with small storage roots. Establishing the crop with rooted transplants instead of slips was satisfactory as long as the transplants were less than 4 weeks old. On the basis of our limited data, the following cultivars and selected lines may be suitable for Quebec, Canada: Beauregard, B94-24, Evangeline, Georgia Jet, GJ2010, and Murasaki-29. ‘Evangeline’ and ‘Covington’ had higher soluble solid contents than the other cultivars. High percent soluble solids may be desired by consumers. In spite of the absence of pesticides, very few pest or disease problems were observed except for some postharvest soft rot.