Maryland Tree Architecture Project

Volume 67 Number 3 Article 5 Pages: 168-174

Year 2013 Month 7
Title: Effects of the Phenotype and Seed Parent on the Size, Productivity and Fruit Quality in Second-Generation Seedling Apple Trees
Authors: Julia M. Harshman, and Christopher S. Walsh
Citation
Abstract:
First-generation seedling apple trees derived from ‘McIntosh Wijcik’ (Malus × domestica Borkh.) were used as putative pollen parents to generate seed using ‘Cripps Pink’ and ‘Fuji’ as seed parents. Seeds from this open pollination were stratified, germinated, grown in the greenhouse, overwintered under cover and planted in the field. During their juvenile years, the seedling trees were sorted into two phenotypic categories: 1) trees exhibiting the wild-type phenotype typical of ‘Cripps Pink’ and ‘Fuji’, and 2) trees with an apparent columnar phenotype. Trees that had been identified with the ‘Wijcik-like’ phenotype were smaller than wild-type trees. Although they were smaller and yielded less fruit, they were found to be more efficient. No statistically significant interactions of cultivar and phenotype were noted for either tree size or efficiency. This research demonstrates that significant scion-dwarfing can occur in ‘Wijcik-type’ trees with enhanced yield efficiency. Harvest date, size and length-todiameter ratio were similar for fruit of both tree phenotypes and for both cultivars. Fruits from wild-type seedling trees were firmer, with higher soluble solids concentration (SSC) and a lower starch index than fruits from ‘Wijcik-type’ apple seedling trees. Apple scions with the greater height-to-spread ratio found in the ‘Wijcik-type’ phenotype could be applicable to the tall-spindle production system currently in vogue in North America. One of the major expenses to growers - labor - could be reduced significantly with the eventual development of scion varieties that are more efficient and naturally develop a more desirable architecture.