Differential Growth Responses of Apple Species to Chilling and Root Pruning

Abstract

Malus dometica Borkh., M. anis, M. prunifolia Borkh., M. × robusta Rehd., M. antonovka, M. borwinkw, and M. ranetka bare-root seedlings were chilled at 5C for 0, 400, 800, 1200, or 1600 hours. After chilling treatments, one-half of the seedlings were root-pruned and all seedlings were placed in a greenhouse for 15 days. Quantitative differences between species in the timing and magnitude of new root and shoot growth responses to chilling were observed. Root pruning decreased and delayed the production of roots <0.6 mm in diameter in response to chilling, while the production of larger roots was less affected. Regeneration of both root types differed among species. For new large (≥ 0.6 mm in diameter) root growth criteria, interactions between chilling hours and species were apparent. Chilling requirements and growing degree hour requirements for vegetative budbreak of each species were estimated.