A transgenic apple callus showing reduced polyphenol oxidase activity and lower browning potential

Polyphenol oxidase (PPO) is responsible for enzymatic browning of apples. A pples lacking PPO activity might be useful not only for the food industry h ut also for studies of the metabolism of polyphenols and the function of PP O. Transgenic apple calli were prepared by using Argobacterium tumefaciens carrying the kanamycin (KM) resistant gene and antisense PPO gene. Four KM- resistant callus lines were obtained from 356 leaf explants. Among these tr ansgenic calli, three calli grew on the medium containing KM at the same ra te as non-transgenic callus on the medium without KM. One callus line had a n antisense PPO gene, in which the amount and activity of PPO were reduced to half the amount and activity in non-transgenic callus. The browning pote ntial of this line, which was estimated by adding chlorogenic acid, was als o half the browning potential of non-transgenic callus.