Investigations to Determine Rootstock Cultivar Performance for Sustainable Apple and Bunch Grape Production in Alabama

Abstract

Evaluating various scion-rootstock combinations in local environmental conditions is critical to gain further insights and knowledge on vine vigor for sustainable production in the southeast. Very little is known concerning vegetative growth, productivity, fruit quality, and overall performance of grape rootstocks in central Alabama and the potential vine Pierce’s Disease (PD) resistance, drought and nematode resistance, and other biotic and abiotic challenges common to the southeastern environment. The main objective of the present study was to determine best suited rootstocks for enhanced sustainability of hybrid bunch grape production in Alabama and the southeast. The experimental vineyard was established in 2014 and data collected during 2017-2018. Experiment consisted of six rootstock-scion combinations: own-rooted ‘Chardonel’, ‘Chardonel’ grafted on ‘1103P’ rootstock, own-rooted ‘Norton’, and ‘Norton’ grafted on ‘1103P’, ‘5BB’, and ‘5C’ rootstocks. Total yield per vine of ‘Chardonel’ grafted on ‘1103P’ was higher than the yield of own-rooted control vines. ‘Norton’ grafted on ‘1103P’ had the highest pruning weight per vine, while ‘Norton’ grafted on ‘5BB’ had the lowest. Our preliminary results indicate that ‘1103P’ grafted ‘Chardonel’ produced higher yield and larger cluster size in comparison to own-rooted ‘Chardonel’ vines. Rootstocks ‘1103P’, ‘5BB’, and ‘5C’ did not affect fruit quality, and yield of ‘Norton’ grape. ‘Norton’ grafted on ‘5BB’ did not performed well based on symptoms of vine decline and low survival rate in the Alabama environment during the period of present study. Fire blight (FB) (Erwinia amylovora) disease management costs are estimated at approximately $100 million a year in the USA. Newly released FB resistant apple rootstocks can aid in disease management and improve production sustainability. Semi-dwarf and dwarf size-controlling rootstocks are available and utilized in high density orchards, but their effects on plant vigor, production efficiency and fruit quality have not been established in the Alabama environment. The objective of this study was to determine the best performing apple rootstocks using an innovative cultivation system. In 2014, as part of the NC-140 Regional Research Project, an experiment was established at the Chilton Research and Extension Center (CREC) Clanton, using ‘Aztec Fuji’ apple grafted on fourteen newly released rootstocks: ‘V.1’, ‘V.5’, ‘V.6’, ‘V.7’, ‘G.11’, ‘G.30’, ‘G.41’, ‘G.202’, ‘G.214’, ‘G.935’, ‘G.969’, ‘M.9-T337’, ‘B.10’, and ‘M.26 EMLA’. Our results suggest ‘G.969’ and ‘G.214’ are promising rootstocks for Alabama conditions based on total yield and yield efficiency during the study period. Trees grafted on ‘G.202’, ‘G.214’, and ’G.935’ produced the sweetest fruit. ‘G.202’ trees 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, but were the most vigorously growing rootstocks in the present study, and may not be a good choice of size-controlling rootstocks for a high density apple orchard system in Alabama. Multiple year evaluations will be needed to obtain a more thorough understanding of rootstock effect on apple tree size, production efficiency, and overall performance in Alabama.