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Abstract
Two distinct syndromes have emerged in some production areas that have caused losses of sweetpotato (Ipomoea batatas) storage roots during postharvest storage: a complex of fungal rots (end rots) progressing from either end of storage roots and a necrotic reaction (internal necrosis) progressing internally from the proximal end of storage roots. This study was conducted in multiple environments to evaluate whether the use of preharvest ethephon application and storage with or without curing after harvest could be used to screen sweetpotato breeding lines for susceptibility/resistance to these two disorders. Treating vines with ethephon 2 weeks before harvest and placing harvested roots directly into storage at 60 °F without curing resulted in the greatest incidence of end rots in each state and there were significant differences in incidence among the sweetpotato genotypes evaluated. However, when ethephon was not used and roots were cured immediately after harvest, the incidence of end rots was low in all the genotypes evaluated except for one breeding line. Incidence and severity of internal necrosis were greatest when ethephon was applied preharvest and roots were cured immediately after harvest, but two cultivars, Hatteras and Covington, had significantly more internal necrosis than all others.
Production and consumption of sweetpotatoes has steadily increased in recent years as recognition of their benefits to a healthy diet and availability of more diverse products has increased (U.S. Department of Agriculture, 2011). The need to continually supply both fresh and processing markets has increased simultaneously, resulting in increased need to store sweetpotatoes for up to 1 year. Given the high cost of both production and storage of sweetpotatoes, it is essential for producers to pack out as great a proportion of the stored sweetpotatoes as possible. Sweetpotatoes are routinely cured immediately after harvest by holding them for 4 to 7 d at 85 °F and 90% relative humidity (RH) to promote healing of wounds incurred during harvest, thus reducing microbial infection and water loss during storage (Clark et al., 2013a). In addition, recent research suggests that chemical defoliation before harvest may increase skin adherence and reduce skinning during harvest and subsequent handling (Schultheis et al., 2000; Wang et al., 2013).
In the past 5 to 10 years, two problems have emerged in some locations that...