Fruit Growth Characteristics and Chronological Development of Calyx-End Splitting in Pacific Rose™ Apple

Abstract

Calyx-end splitting (CES) is a preharvest physiological disorder, which downgrades the quality of Pacific Rose apple fruit, but its causes are not known. Fruit growth characteristics and incidence of calyx-end splitting were monitored on Pacific Rose apple. The onset of splitting incidence was at 20 weeks after full bloom (WAFB) and increased progressively with maturity. Fruit growth (diameter, length, and volume) followed an exponential growth pattern. The absolute growth rates (AGR) of diameter and length fluctuated, but snowed a declining trend over time, whereas the volume AGR increased until 17 WAFB and declined thereafter. Fruit diameter, length, and volume relative growth rates (RGR) declined exponentially over time. Fruit shape (length/diameter ratio) was characterized by three distinct phases, corresponding to rapid decline (until 18 WAFB), stagnation (18-21 WAFB), and slow rise during the last few weeks before commercial harvest. The onset of CES was preceded by a period of maximum AGR of fruit volume during which fruit shape changed very little. The growth curves of fruit diameter, length and volume respectively, however, did not provide any distinct period with regard to the onset of fruit splitting in the orchard.