Peroxidase activity and superficial scald development in apple fruit

The relationship between soluble peroxiclase (EC 1.11.1.7; POX) activity and the development of a chilling-related disorder, superficial scald, was studied in three apple fruit (Malus x domestica Borkh.) systems: a White Angel x Rome Beauty population with progeny with different scald susceptibilities; Delicious from three harvests with progressively declining scald susceptibility; and the scald-resistant Idared and the scald-susceptible Law Rome. Differences in incidence and severity of scald in progeny from White Angel x Rome Beauty progeny tended to show relationships with POX activity at harvest, but, overall, associations were not consistent. However, greater scald incidence and lower POX activity were found in less mature Delicious fruit than in later harvested fruit. Also, the scald-resistant Idared had a much higher POX activity compared with the scald-susceptible Law Rome. A general hypothesis that POX activity is related to scald susceptibility was generally supported, but exceptions were observed.