Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016
BREEDING TO DEVELOP A PURPLE SWEETPOTATO FOR THE VIRGIN ISLANDS Thomas W. Zimmerman and Carlos Montilla, University of the Virgin Islands Agricultural Experiment Station, RR#1 Box 10,000, Kingshill, VI 00850 email: tzimmer@uvi.edu Keywords: Ipomoea batatas, tuberous roots, Caribbean Abstract Limited work has focused on the nutritionally beneficial purple-fleshed sweetpotato in the Caribbean. Purple-fleshed sweetpotatoes are an excellent source of bioflavonoids and antioxidants. Cultivars of purple-fleshed sweetpotato are common in Asia but seldom grown in the west. These Asian cultivars set tuberous roots along the stem length where they root. The objective of this work was to introgress the purple-fleshed characteristic into highly productive early bearing (90-105 days) lines. The purple-fleshed line ‘VIP’ was used in reciprocal crosses with ‘Bonita’, ‘Liberty’, ‘Mojave’ and ‘Ruddy’. From hand pollination of these hexaploid plants, 179 seedlings were obtained with a skin color ranging from white to deep burgundy. After the first field trial, 60 were selected for further evaluation based on early tuberous root shape and set, weevil tolerance and soluble sugar content. Continued evaluation will reduce selection down to 20 which further scrutiny to narrow selection to the top five. Materials and methods The purple-fleshed sweetpotato line ‘VIP’ was used in reciprocal crosses with ‘Bonita’, ‘Liberty’, ‘Mojave’ and ‘Ruddy’. From hand pollination of these hexaploid plants, 179 seedlings were obtained with a skin color ranging from white to deep burgundy. Seedlings were scored for weevil damage at 90 and 120 days. A refractometer was used to determine the soluble sugar content from freshly squeezed tuberous root pieces at harvest and one week later after curing. Main results A wide range of sweetpotato types were obtained. These included negative attributes as very hairy roots with minimal tuberous root development, deep eyes, irregular tuberous root shape and high susceptibility to sweetpotato weevils. Positive attributes included 80% marketable tuberous roots in 90 days, shallow eyes, evenly curved oblong shape, soluble sugar content at or above 10 after one week post-harvest curing and purple flesh and minimal weevil damage at 120 days. Tuberous root skin color varied and ranged from creamy white to deep crimson burgundy (Figure 1). Tuberous root development ranged from few to above ten with the larger set resulting in smaller roots. The preference was for 5 to 7 marketable roots per plant. Screening over over winter versus summer allowed for evaluation of photoperiod response to tuberous root development. Conclusion Developing an improved purple flesh productive sweetpotato requires multiple crosses to obtained the desired characteristics that are needed for production in the Caribbean. Screening of seedlings over the winter and summer season allows to select for early-bearing day neutral lines. The sweetpotato weevil is a common pest, however selecting for deeper tuberous root set impart better resistance.
Figure 1. Range in sweetpotato skin color from breeding.
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