A multi-location comparison of ‘Geneva® 16’, ‘Geneva® 41’ and ‘M.9’ Apple Rootstocks in North America.

In 1998, two multi-site replicated rootstock trials were established by the US national rootstock testing group, "NC-140". The trials compared 2 elite dwarf Geneva apple rootstocks that are tolerant to fireblight and Phytophthora root rot. The first trial used ‘Jonagold’ as the scion and compared ‘M.9’ with Geneva® ‘G.16’ and ‘G.41’. It was planted at 10 locations across North America. The second trial, which was planted at 9 locations, used Gala as the scion and compared only ‘M.9’ and ‘G.16’. At the end of 6 years, ‘G.16’ produced a tree slightly larger than ‘M.9’ EMLA with Gala, while with Jonagold, tree size was similar to ‘M.9’ EMLA. Productivity of ‘G.16’ was similar to ‘M.9’ in all trials. Trees of Jonagold on ‘G.41’ were slightly, but significantly smaller in size than ‘M.9’ EMLA, yet productivity was similar to ‘M.9’. Yield efficiency of ‘G.41’ was higher, but not significantly different than ‘M.9’ EMLA. At the Geneva NY site, there was no effect of tissue culturing of the stoolbed mother plants used to create the nursery liners of ‘G.16’. Tree size, yield, yield efficiency or root suckers were similar to non tissue culture stoolbeds indicating that with at least this stock, plants can be multiplied by tissue culture to establish stoolbeds without negative effects. Tree survival of ‘G.16’ and ‘G.41’ was better than ‘M.9’ where fireblight caused tree losses. Tree survival of ‘G.16’ was better than ‘M.9’, ‘M.26’ or ‘B.9’ following a mid winter cold event in January 2004 at a Northern NY site. ‘G.16’ is currently being commercialized in the US and Canada. ‘G.41’ will be patented and commercialized in Feb. 2005.