Evaluation of apple rootstocks planted in different locations in South Africa

Challenges faced with apple farming in South Africa include harsh environmental conditions, variable soils, woolly apple aphid, and apple replant disease complex. The objective of this study was to evaluate new dwarfing, semi-dwarfing and semi-vigorous rootstocks from the GENEVA^® range against the South African industry standard rootstocks (MM.109, M.793, and M.7). During the 2013 season, identical apple rootstock trials with 'Fuji' as scion were established at three localities (Oak Valley, Breëvlei, and Helderwater) in South Africa. At each locality, M.9 EMLA, M.9 Nic29, G.222, M.7, MM.109/M.9 EMLA, MM.109/G.222, M.793/M.9 EMLA, M.793/G.222, G.778/M.9 EMLA, and G.778/G.222 were planted in 7 blocks of 3 trees per rootstock as the “more dwarfing site”. M.7, G.202, G.778, M.793, MM.109, and G.228 were planted in 10 blocks of 3 trees per rootstock as the adjacent “more vigorous site”. All trials were established on fumigated sites previously planted to apple and were managed differently, but according to standard commercial practice. The trees at Oak Valley and Helderwater were planted at 4×1.5 m, while those at Breëvlei were planted at 3.5×1.5 m. All trees from all the three farms were assessed for vegetative and reproductive performance. G.778, G.228, G.202, G.222 rootstocks, and G.778 with either G.222 or M.9 EMLA as interstems appeared to be among the most productive rootstock at all three sites whereas the industry standard rootstocks, especially M.793 and MM.109, were among the least productive. These rootstocks have a potential to improve fruit production in the South African apple industry.