Fruit firmness and pectinmethylesterase activity during on-tree ripening of peach

Abstract

Fruit firmness and pectinmethylesterase (PME) activity were determined at 3 harvest dates over 2 weeks for 11 low chill and 5 high chill peach (Prunus persica) varieties of which 11 were melting flesh (mf) (excluding O'Henry) and 4 were nonmelting flesh (nmf) varieties. Firmness decreased in all classes as fruit became more tree ripe. However, there was no apparent relationship between PME activity and major changes in firmness for low vs high chill, or mf vs nmf classes. Thus, on-tree initiation of ripening and softening in peach fruit was not related to PME activity. Levels of PME activity did not fully explain the softening differences between varieties. 'O'Henry' had a slower softening rate than mf varieties and lower PME activity than found at each harvest date in either mf or nmf va
rieties indicating that it has a different flesh type.