Abstract
In order to prevent patented new cultivars from unauthorized cultivation, a DNA analysis technique aimed at identifying sweetpotato cultivars used for making Hoshi-imo, steamed and dried sweetpotato slices, was developed based on retrotransposon insertion polymorphisms. Insertion sites of the Rtsp-1, an LTR (Long Terminal Repeat) retrotransposon identified in sweetpotato genome, were displayed by the S-SAP (sequence-specific amplification polymorphism) technique for 12 cultivars, which included traditional cultivars and advanced breeding lines for Hoshi-imo production. The S-SAP products, which were present for at least one cultivar but were absent for the others, were cloned and sequenced. PCR primers were designed on the host sequences adjacent to Rtsp-1 insertion. Absence or presence of PCR products of nine cloned Rtsp-1 insertion sites could successfully differentiate the 12 cultivars. An anion-exchange column was able to isolate DNA from Hoshi-imo, although the steaming process had led to the formation of DNA fragments with small sizes. The PCR for Rtsp-1 insertion sites, nevertheless, amplified the expected products from Hoshi-imo DNA and correctly identified the cultivar used for Hoshi-imo production.
