Effect of fire blight (Erwinia amylovora) resistant apple rootstocks on 'Aztec Fuji' fruit quality and yield efficiency

Fire blight (Erwinia amylovora) disease management costs are estimated at approximately $100 million a year in the USA. Newly released fire blight resistant apple rootstocks can aid in disease management and improve production sustainability. An apple rootstock study was established at the Chilton Research and Extension Center near Clanton, Alabama in 2014 as part of a multistate NC-140 project aiming to assess 14 newly developed fire blight resistant, size-controlling rootstocks grafted with a low-chill ‘Aztec Fuji’ apple. Studied rootstocks include the following newly released cultivars and controls: ‘B.10’, ‘G.11’, ‘G.202’, ‘G.214’, ‘G.30’, ‘G.41’, ‘G.935’, ‘G.969’, ‘M.26 EMLA’, ‘M.9-T337’, ‘V.1’, ‘V.5’, ‘V.6’, and ‘V.7’. Trees are arranged in a RCBD with ten single tree replications and trained to the highly efficient Tall Spindle training system that has not been tested in Alabama before. Tall Spindle is designed to control the vegetative vigor and optimize the crop production especially in the early stage of tree establishment, while providing early returns to the grower. Our results suggest trees grafted on ‘G.202’, ‘G.214’, and ‘G.935’ produced the sweetest fruit. Trees on ‘G.202’ also had an advanced fruit maturity in comparison to other rootstocks in this test. The Vineland series of rootstocks ‘V.5’, ‘V.6’, and ‘V.7’ produced relatively high total yield, and were the most vigorously growing rootstocks in the present study, therefore may not be a good choice of size-controlling rootstocks for a high-density apple orchard system in Alabama. Based on total yield tree^-1 and yield efficiency responses during the study period, ‘G.969’ and ‘G.214’ are considered promising rootstocks for Alabama conditions. Research is going to continue to assess the production efficiency and fruit quality as a way to achieve more efficient land use and sustainable apple production.