Effect of Shade on Pear Fruit Growth and Quality

Abstract

This investigation was undertaken to determine the response of pear fruit growth and quality to shade imposed during development. Whole branches of mature `Bartlett' trees on P. communis L. growing at the Experimental Farm on a sandy loam soil were covered with a 20% transmission black, neutral-density shadecloth from 43 days after full bloom (DFB) to 138 DFB, during the 1995–96 growing season. Two comparable branches on each of five uniform trees were selected for good exposure and one branch of each pair was shaded. Fruit diameters were measured at 2-weekly intervals. Pulp pressure and soluble solids concentration (SSC) were measured at harvest time on 31 Jan. Specific leaf mass (SLM) also was recorded (leaf dry mass was obtained by drying discs at 80°C). Relative fruit growth rates were initially similar between light regimes, becoming lower for the shaded fruit at the subsequent measurements. Light exposure induced a 8.76% increase in final fruit diameter (66.40 mm); this increment would appear to depend on carbohydrate availability, since highly significant differences at P ≤ 0.01 emerged in the spur SLM of the exposed and covered branches (7.68 vs. 5.79 mg·cm–2, respectively). SCC was similar for the two light environments, while flesh firmness was 8.80% higher in the shaded fruit. Our results indicate that solar radiation deprival had clearly detrimental effects on fruit growth and maturity, and they provide a basis for improving pruning and training practices in the future.