THE GENEVA SERIES OF APPLE ROOTSTOCKS FROM CORNELL: PERFORMANCE, DISEASE RESISTANCE, AND COMMERCIALIZATION

The Geneva series of apple rootstocks has been bred for tolerance to fire blight and Phytophthora root rot, high yield efficiency and good tree survival.
Four clones from the program have been released. ‘Geneva^TM 30’ rootstock, which produces a tree about 50% the size of seedling, has continued to show good resistance to fire blight, high yield efficiency in several field plantings on growers farms and in the US national rootstock testing program.
However, it has shown graft union brittleness with ‘Gala’. ‘G.30’ also has the deficiency of producing many lateral spines on stoolbed shoots.
This has limited its production by commercial stoolbed operators. ‘Geneva^TM 16’, which produces a tree about 30% the size of seedling, has been slightly more vigorous than ‘M.9NAKB337’, but has been equally productive.
It has shown very high resistance to fire blight.
It has had excellent performance in the nursery except where virus infected scionwood has been used.
Tests have shown that ‘G.16’ is sensitive to one or more latent viruses. ‘Geneva^TM 11’ rootstock, which produces a tree about 40% the size of seedling, has shown very high productivity and good tree survival, but not immunity to fire blight.
A field planting of ‘Gala’ on ‘G.11’ showed 25% tree loses when inoculated with fire blight while ‘M.9’ and ‘M.26’ trees showed 80–100% tree death. ‘Geneva^TM 202’, which is being commercialized in New Zealand, produces a tree about 40% the size of seedling.
In addition to having high fire blight resistance, it is also woolly apple aphid resistant.
In 2004, we expect to release two additional rootstocks: ‘Geneva^TM 3041’ and ‘Geneva^TM 5935’ which are both fire blight resistant, extremely productive and produces trees 30% and 50% the size of seedling, respectively.