Screening of Ornamental Sweetpotato (Ipomoea batatas) Cultivars for Intumescence Development

Ornamental sweetpotato (Ipomoea batatas) is an herbaceous ornamental crop commonly produced in greenhouses.  The species has been increasingly popular, with several new cultivar introductions in recent years because of its trailing growth habit and striking foliage colors and shapes.  However, the species is susceptible to developing intumescences—a physiological disorder characterized by abnormal, translucent outgrowths on the leaf surface with a gall or wart-like appearance. Ultimately, this disorder results in the death of the affected cells. With many recent introductions, we conducted a screening trial with 36 ornamental sweetpotato cultivars to 1) describe and characterize foliage type and plant growth; and 2) document intumescence development and severity of each cultivar.  Each leaf on each plant was rated for intumescence development on a scale from 0 to 5 (0 = no intumescence and 5 = severe) after six weeks of production in a glass greenhouse.  Nearly half (47%, n=17) of the cultivars exhibited some level of intumescence development. The cultivar ‘Blackie’ had the highest average rating of 2.27, while most cultivars that developed intumescences had an average rating of 1.5 or less.  Cultivars ‘Blackie’ (67%), ‘Sweet Caroline Bronze’ (35%) and ‘South of the Border Chipotle’ (34%) had the highest percentage of their total number of leaves exhibiting intumescences.  Nineteen cultivars were non-symptomatic for intumescence occurrence, including ‘Sidekick Black Heart’, a compact substitute for ‘Blackie’ and ‘Black Heart.’ No relationship was observed between leaf color, shape, or plant habit and intumescence occurrence. This practical information may aid greenhouse growers in selecting ornamental sweetpotato cultivars for production in an effort to avoid this disorder.