ABSOLUTE AND RELATIVE GROWTH RATES AS INDICATORS OF FRUIT DEVELOPMENT PHASES IN SWEET CHERRY Prunus avium

Abstract

Fruit size is a quality parameter that has a direct effect on economic profitability of sweet cherry orchards. However, there are few studies on the physiological indicators that can allow managing this parameter in sweet cherry. The aim of the present resarch was to analyze growth rate and cell development as indicators of fruit growth patterns in ‘Bing’ sweet cherries. Absolute growth rate (AGR, g day-1) and relative growth rate (RGR, mg g-1 day-1) were estimated from 14 to 77 days after full bloom (DAFB). Cell density (number mm-2) and cell length (µm) in the mesocarp were also determined. The
highest AGR value (0.07 g day-1) was recorded at 58 DAFB, coinciding with full fruit cell expansion (phase III), while the highest RGR value (174 mg g-1 day-1) was reached at 23 DAFB, coinciding with fruit cell division reduction (end of phase I). AGR was significant and positively related (R² = 0.85*) to cell length, but negatively related to cell density (R² = 0.78*). However, no significant relationship was found between RGR and the cell parameters under study. The obtained results suggest that AGR and RGR are good indicators to estimate both timing and length of fruit growth phases in sweet cherry. Cellular changes in cherry fruit during tree growth are best explained by the AGR.