Noro et al. (1988) found that, although all the cultivars investigated showed a great increase
in sucrose and a decrease in malic acid during the color formation, no difference in
the changes of these substances was found between red (‘Jonathan’, ‘Starking Delicious’,
‘Tsugaru’ and ‘McIntosh’) and yellow (‘Golden Delicious’ and ‘Mutsu’) apple cultivars. In
the present study, during the color formation, the apple cultivars ‘Starkrimson’ and ‘Golden
Delicious’ of Maoxian had higher (P ≤ 0.01) contents of reducing and non-reducing
sugar, and lower (P ≤ 0.05) contents of malic acid and water in the peels than those
of Ya’an. Within the same habitat, no significant difference in concentrations of reducing
and non-reducing sugar, malic acid and water was found in the peels of ‘Starkrimson’
and ‘Golden Delicious’ apple. The regression analysis further suggested that PAL activity
and reducing sugar content were related to anthocyanin accumulation in the skin of
apple.