Influence of four apple cultivars on five dwarfing rootstocks on morphology of two-year-old limb sections

Morphological characteristics on two-year-old stem sections of four apple c ultivars on five dwarfing rootstocks (M.26 EMLA, O.3, M.9 EMLA, B.9, Mark) were measured in Wooster, OH, Manhattan, KS and Wichita, KS from 1994-1996. Location and year had the greatest influence on all the morphological char acters. Rootstock had minor influence on morphological characters measured, while cultivar had a significant influence. Stem length of all cultivars a nd rootstocks was positively correlated to spur and shoot numbers. For most of the cultivars and rootstocks, yield was positively correlated with dens ity for flowering spurs and negatively Correlated with stem length. Consist ently for all cultivars M.26 EMLA and O.3 produced the longest stems and ha d the most spurs/stem, while the opposite was true for MARK and B.9/ the da ta in this study supports the theory that rootstock controls total growth a nd cultivar controls distribution of growth. However, the cultivar rootstoc k interactions show that some rootstocks were able to cause slight changes in the distribution of growth of a given cultivar.