Cropload Management and Appropriate Harvest Timing Improves Final Fruit Size and Fruit Quality of US 71655-014, a New Fire Blight Resistant European Pear Selection, Poster Board #304

US 71655-014 (‘Gem’) is a fire blight resistant pear selection developed at the USDA Appalachian Fruit Research Station. Despite possessing several positive attributes [precocity, high annual production, attractive fruit appearance, fire blight resistance, good storability and consumer acceptance], ‘Gem’ is a small-fruited genotype.  The Pacific Northwest pear industry prefers large-fruited cultivars (exceeding 200 g).  We, therefore, examined two strategies to improve fruit size of ‘Gem’.  First, a two-year cropload study was initiated on sixth leaf trees.  Croploads were established by thinning at 50 days after full bloom to four cropload levels based on the number of fruit per cm² of trunk cross-sectional area (TCA):  T1) 8–10 fruit per cm² TCA, T2) 6–8 fruit per cm² TCA, T3) 2–4 fruit per cm² TCA, and T4) commercially thinned to ‘Bartlett’ standards (3-5 fruit per cm² TCA, determined after thinning).  Fruit weight at harvest was 150 g, 171 g, 208 g and 203 g for T1, T2, T3, and T4, respectively.  Frequency distribution of larger fruit size classes was markedly improved for T3 and T4.  Individual tree yields averaged 30 kg for T3 and T4; roughly half of T1.  However, canopy volume and TCA of T3 and T4 indicated that trees could be planted at higher densities to attain adequate yields of high-quality fruit.  Return bloom and fruit load was not significantly affected by cropload, in either year.  Cropload level strongly predicted fruit weight at harvest and could serve as a production management tool to target fruit weight for a given market.

In 2011, we examined the role of harvest maturity on fruit size and quality following cold storage and ripening.  Fruit were harvested weekly for 4 weeks.  The initial harvest occurred when fruit attained a previously identified fruit firmness (FF) value coinciding with maximum storability (~7 months).  At each harvest, fruit was weighed, placed in regular atmosphere storage (–1 °C), and evaluated monthly for 7 months.  Fruit quality attributes [FF, soluble solids, total acids, extractable juice, and fruit weight] were assessed upon removal from cold storage.  An additional sample per replication was ripened for 7 days at 20 °C and evaluated for quality attributes. Fruit size was markedly improved with delayed harvest dates.  Although ‘Gem’ is not a melting pear, ripened fruit softened and extractable juice decreased as duration in storage increased, irrespective of harvest timing.  Changes in fruit quality attributes relative to harvest maturity and storage duration will be presented.