Rapid shoot regeneration in industrial 'high starch' sweetpotato (Ipomoea batatas L.) genotypes

Sweetpotato (Ipomoea batatas L.) is an important crop in North Carolina with annual production of 0.33 million tons, accounting for 37% of total US supply (USDA, Louisiana Farm Reporter 8(12), August 2008). To target industrial use, novel high-starch industrial-type varieties that contain more than 30% dry matter were developed by conventional breeding methods. In vitro cultures from selected genotypes were established using meristem culture. To establish regeneration procedures that could be coupled with transformation experiments, conditions for the induction of rapid shoot-organogenesis in leaf explants were compared using varying concentrations of the auxins 'NAA', 'IAA', '2,4-D', and '4-FA' either alone or in combination with zeatin riboside. Regeneration efficiencies, defined as the number of explants developing shoots out of the total number tested, were as high as 57% for the best genotypes, with a significant genotype-dependent response observed in all the hormone regimes evaluated. In all treatments, shoot regeneration was observed within 2 months. Our results led to the establishment of optimized in vitro regeneration procedures for the novel high-starch sweetpotato (SP) genotypes 'DM01-158', 'FTA94', 'FT489', and 'PDM P4' that are rapid and reliable.