Comparison of polyphenol oxidase in tubers ofSolanum tuberosum and the non-browning tubers ofS. hjertingii

Solarium hjertingii, a wild potato species, does not exhibit enzymatic browning nor blackspot. Blackspot and enzymatic browning are physiological disorders that are caused by the reaction of the enzyme polyphenol oxidase with phenolic substrates, resulting in discoloration of tuber cortex. We determined thatS. hjertingii has a low amount of at least one of the polyphenol oxidases in its tubers compared toS. tuberosum. Less than 5 μg ofS. tuberosum polyphenol oxidase protein, as determined from Western blot staining, had measurable enzymatic activity. In contrast,S. hjertingii protein with comparable staining had no detectable activity.