Fruit growth characteristics and chronological development of calyx-end splitting in Pacific Rose (TM) apple

Calyx-end splitting (CES) is a preharvest physiological disorder, which dow ngrades the quality of Pacific Rose(TM) apple fruit, but its causes are not known. Fruit growth characteristics and incidence of calyx-end splitting w ere monitored on Pacific Rose(TM) apple. The onset of splitting incidence w as at 20 weeks after full bloom (WAFB) and increased progressively with mat urity. Fruit growth (diameter, length, and volume) followed an exponential growth pattern. The absolute growth rates (AGR) of diameter and length fluc tuated, but showed a declining trend over time, whereas the volume AGR incr eased until 17 WAFB and declined thereafter Fruit diameter, length, and vol ume relative growth rates (RGR) declined exponentially over time. Fruit sha pe (length/diameter ratio) was characterized by three distinct phases, corr esponding to rapid decline (until 18 WAFB), stagnation (18-21 WAFB), and sl ow rise during the last few weeks before commercial harvest. The onset of C ES was preceded by a period of maximum AGR of fruit volume during which fru it shape changed very little. The growth curves of fruit diameter, length a nd volume respectively, however, did not provide any distinct period with r egard to the onset of fruit splitting in the orchard.