Cultivar Adaptability for Midwest Sweetpotato Production

Sweetpotato, Ipomoea batatas L., is a warm-season vegetable crop that is widely grown mainly in the southern parts of United States. In the Midwest, short growing season often limits the production of this crop. Cultivar selection and management practices could play an important role in the proper establishment, growth, and development of sweet potato crop. This study investigated the role of cultivar selection for sweetpotato production in Iowa. Study was conducted at the Horticulture Research Station, Iowa State University, Ames, IA, and was set up as a randomized complete-block design with four replications. Treatments comprised of five sweet potato cultivars: Beauregard, Covington, Diane, Evangeline, and Hernandez. Sweetpotato slips were planted on raised beds covered with black plastic mulch on 1 June 2012. Each treatment had three 6-m long beds. Beds were spaced 183 cm center-to-center. Spacing between plants was 23 cm. Roots were harvested on 5 October, 2012, and cured at 27 °C and a relative humidity of 80% to  90% for 14 days. Yield of Jumbo grade and Grade 1 roots were higher for ‘Beauregard’ (16,432 kg/ha) and ‘Evangeline’ (20,284 kg/ha) as compared to other cultivars. ‘Beauregard’ has been a standard workhorse cultivar in sweetpotato growing areas of United States.  ‘Evangeline’ is a relatively new cultivar with characteristics similar to those of ‘Beauregard’ but with southern root-knot nematode resistance and higher sucrose content. For Grade 1 roots there was no statistically significant difference between ‘Covington’ and ‘Beauregard’. ‘Diane’ produced the lowest yield for Grade 1 roots (7,530 kg/ha). There were no statistically significant differences in yield for grade 2 roots among treatments. Cull yield was lowest for ‘Covington’. Roots with odd or abnormal shapes were higher in ‘Hernandez’ and ‘Diane’ as compared to ‘Covington’ or ‘Evangeline’. Root quality in terms of average root length indicate no statistically significant difference among cultivars, however, average root width was significantly different among cultivars with highest width for ‘Beauregard’. Average root width was lowest in ‘Diane’. Laboratory analysis of crushed sweetpotato roots showed highest sugar concentration in the cultivar ‘Hernandez’. ‘Beauregard’ had the lowest sugar content. Results from this study indicate that cultivar selection is critical when considering sweetpotato production in the Midwestern region. ‘Evangeline’, ‘Beauregard’, and ‘Covington’ seem to be promising cultivars for sweetpotato production in the Midwest region