Characterizations of "reddish-pulp", a physiological disorder of peach fruit

Five peach (Prunus persica Batsch) cultivars were characterized for the "reddish-pulp" physiological disorder in which the flesh of mature fruit undergoes a pink to red discoloration. Fruit exhibiting this disorder had high contents of anthocyanin and phenolic compounds. The degree of "reddish-pulp" development had a negative significant correlation (P<0.001) with flesh firmness and had no clear relationship with fruit weight and total soluble solids content. Furthermore, there was no significant difference in the rate of "reddish-pulp" development among cultivars and orchards. However, there was a large difference in the rate of "reddish-pulp" occurrence; with some trees almost 100% of the fruits exhibited the symptom, whereas fruits from other trees expressed a very low percentage, irrespective of the orchard. The degree of "reddish-pulp" in the fruit harvested from trees showing a high rate of discoloration increased after storage at 25°C compared to the fruit harvested from trees showing little or no symptoms of the disorder. The annual difference in both trees, showing high and low rates of "reddish-pulp" occurrence, was small. However, once "reddish-pulp" fruit appeared in a tree, such trees produced fruit with "reddish-pulp" in subsequent years. When the dry weight contents of roots from trees with high and low rates of "reddish-pulp" occurrence were compared in autumn, the former weighed less than the latter probably because it had fewer roots, especially fine roots of less than 2 mm in thickness. Based on these observations the possible cause(s) of the development of "reddish-pulp" in peach fruit is discussed.