Abstract
Orchard-side optimization of fruit quality is experiencing renewed research focus in the fresh fruit industry as new technologies and quality metrics have emerged to enhance consumer acceptance and satisfaction. Fruit dry matter, one such quality index gaining traction among numerous fresh fruit commodities, was targeted for improvement in d’Anjou pear with the application of seasonal pruning cycles (fall, fall and summer, winter, and winter and summer) across two growing seasons in 2016 and 2017 in a mid-aged, traditionally managed commercial orchard in the Columbia basin, Washington, USA. Dry matter was assessed non-destructively on pears using near-infrared spectroscopy at harvest and fruit categorized in to low (<13%), moderate (13–16%), and high (>16%) dry matter quality categories, revealing that fall pruning positively impacted average predicted fruit dry matter in comparison to winter pruning (15.1 vs. 14.2% in 2016 and 13.7 vs. 13.1% predicted dry matter in 2017 for winter vs. fall pruning, respectively), as well in the abundance of high dry matter fruits. The addition of summer pruning to either fall or winter pruning increased fruit size by up to 13% of proportion of fruits 80 mm or greater in diameter. Further, a tendency for summer pruning to decrease yield (up to nearly 30 kg/tree lower yields), average fruit dry matter (up to 0.5% lower average predicted dry matter), and abundance of high dry matter fruits (up to 11% fewer high predicted dry matter fruits) was observed. Fruit quality classes assembled on predicted dry matter verified the utility of this emerging parameter as a fruit quality metric for pears as demonstrated by more desirable post-harvest eating characteristics such as higher soluble solids content corresponding to greater at-harvest predicted dry matter categories. Targeted seasonal pruning in association with precise at-harvest dry matter fruit sorting may preserve the profitability of pear cultivation through their impact on fruit quality and associated consumer experiences.
Highlights
The North American pear industry is dominated by traditional orchard plantings, cultural practices, and low-input technologies [1,2]
For treatments coupled with summer pruning, winter and summer (W+S) pruning resulted in significantly higher amounts of both leaf materials and first year shoot removed relative to fall and summer pruning (F+S, Figure 2)
Summer pruning in combination with either fall or winter pruning averaged 0.5 and 0.2% lower predicted dry matter in F+S pruning treatment relative to F pruning alone in 2016 and 2017, respectively, and 0.1 and 0.3% lower predicted dry matter for W+S pruning compared to W pruning alone in 2016 and 2017, respectively (Figure 5)
Summary
The North American pear industry is dominated by traditional orchard plantings (non-trellised, low- to medium-density plantings), cultural practices, and low-input technologies [1,2]. Low-density systems retain their viability in growing districts in the Pacific Northwest (PNW) where the use of modern dwarfing Quince rootstocks remains inadvisable due to winter frost risk and graft incompatibility issues [1,3,4]. These limitations on the use of dwarfing Quince rootstocks in pear cultivation in the PNW has resulted in the persistence of central- or multi-leader, open-vase orchards grafted on pear seedlings characterized by vigorous growth and dense canopies with wide variability. Dry matter, emerging as a reliable quality index among numerous tree fruit commodities, is a measure of the amount of photosynthates (sugars) and derivative compounds (starches, proteins, structural carbohydrates, etc.) acquired from the leaves during photosynthesis as well as roots by nutrient uptake and transported to the fruit for storage and metabolism [12,13]
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