A generalized scaling approach to improve variety selection in orchard fruit Zachary T. Brym, Dept. of Biology and Ecology Center, Utah State University A Scaling Approach Scaling is the description of universal patterns. Scaling relationships between morphological characteristics, like branch diameter, and biomass are consistent within and among all plants. Scaling patterns illustrate physiological similarities among plants. Orchard fruit trees scale like natural trees! Previous research suggests universal scaling relationships described for natural trees hold up in domesticated tart cherry and apple trees. Small scaling differences distinguish varieties. Despite broad conservation of scaling among plants, relatively small differences in scaling exponents might reveal useful physiological divergence among varieties. Scaling Approach Feedback Loop As small differences in scaling help inform selection of varieties for further research and commercial planting, consistent differences among certain relationships can reveal important levers for developing and evaluating new varieties and orchard systems. A Weecology Production Acknowledgements Project funding provided by the Utah State University Graduate Student Senate Research and Project Grant, the Ecology Center Ph.D. Assistantship and Research Support Award, and the Office of Research and Graduate Studies Doctorial Dissertation Enhancement Grant. Field support from the staff and researchers at the Kaysville Experimental Orchard and USU undergraduates Josh Anderson and Josh Shugart greatly influenced the project’s sample size. Standardized Scaling Exponents Estimated by Rootstock Exponents are standardized to ‘All-branch’ estimation (0). Overlapping 95% CI means no difference. Step 1: Locate Differences Among Rootstocks / Populations Variance in CI of Allometric Exponents Research Questions What are the differences in scaling exponents among apple rootstocks in a rootstock selection trial? Are differences in scaling exponents related to fruit production and yield? Experimental System 2002 Golden Delicious Rootstock Trial NC-140 Regional Rootstock Research Project Kaysville Experimental Orchard, Utah State University Apple: Malus x sylvestris var. domestica 3.5 x 5.5 m spacing, Vertical Axe training system Key Findings Branch metrics strongly relate to cumulative yield. Maximum Branch Path Length R 2 = Total Number of Pruning Scars R 2 = Variation in estimated allometric exponents also relate strongly to cumulative yield. Mass ~ Diameter at Segment-level R 2 = Mass ~ Volume at Path-level R 2 = CG.6210 (aka, Geneva ® 210) consistently produces higher yield than would be expected by body size. Top Predictions of Cumulative Yield by Rootstock Rootstocks that appear above the dashed line produce higher yield than expected by body size feature. Average Branch Metrics Cumulative Yield Step 2: Correlate Significant Differences Branch Metrics & Allometry vs Cumulative Yield ***Letters denote groups with significant differences in means determined by a Duncan’s Multiple Range Test following ANOVA.