(128) Effect of 2,4-DP Concentration on Fruit Drop Control and Maturation of `Braeburn' Apples

Abstract

<jats:p>Apple fruit abscission shortly before harvest is a frequent, recurring problem, thereby reducing potential yield. The synthetic auxin 2 (2,4-dichlorophenoxy) propionic acid (2,4-DP) was evaluated for its effect on reducing fruit drop and influencing ripening of `Braeburn' apples, in the High Valley region of Río Negro, Argentina (38°56'S, 67°59'W). Thirteen-year-old apple trees grafted on MM 111 rootstock were sprayed on 4 Mar. 2005, at 162 days after full bloom (DAFB) with 2,4-DP at doses of 0.05% and 0.10% (v/v), applied with an airblast sprayer, until runoff. Each tree was trained to palmette and planted in a single row from north to south with spacing of 2.3–4.0 m. The following measurements were performed: a) accumulated fruit drop, twice per week and b) maturity indices, weekly. Samples of uniform-size fruits were assessed for maturity (n = 20 per date and treatment), from 167 (commercial harvest) to 195 DAFB. On 23 Mar. (at 181 DAFB), cumulative fruit drop for control treatment was 19.9%, whereas 2,4-DP significantly reduced it to 4.90% and 2.94% at 0.05% and 0.10% (v/v), respectively. Reduction in the drop was also significant later, and 2,4-DP at both doses controlled drop comparably. The synthetic auxin did not affect fruit quality and maturation, based upon flesh firmness, starch degradation, and soluble solids concentration. We conclude that 2,4-DP is an effective drop control compound and it is useful as a management tool to increase yield by reducing fruit abscission and to extend the harvesting window of `Braeburn' apples, since it does not affect ripening. Delaying harvest may provide flexibility for scheduling of labor, fruit processing and packaging, cold storage, and marketing.</jats:p>

A Non-Linear Logistic Model Describing the Diameter Kinetics of 'Braeburn' Apples, as a Function of Time From Full Bloom

“…This indicates that specific fruit growth curves are required according to particular cultivar, soil, climate and orchard (Ortega et al, 1998). Several factors affect final fruit size such as cell number, cell size, intercellular spaces and rate of cell division, time and severity of thinning, pruning, temperature, irrigation and light stress (Garriz et al, 1999(Garriz et al, , 2000(Garriz et al, , 2001(Garriz et al, , 2006(Garriz et al, , 2010. Kaack and Lindhard Pedersen (2010) showed that apple fruit diameter was significantly affected by two climate factors: 1) degree days and 2) evaporation potential.…”