JUVENILITY AS A POSSIBLE CAUSE OF VARIATION IN THE NEW APPLE VARIETY KARMIJN DE SONNAVILLE

A variation in growth and flowering between heat-treated virus-free plants of Karmijn de Sonnaville was studied. Abnormal trees on virus-free M.9 rootstock grew more vigorously and flowered much less abundantly than normal trees. The variability within this variety was also observed in commercial orchards. In this case the buds of the variety were directly from the original seedling, but on virus-infected M.9 rootstock. The abnormal behaviour was not corrected by heat therapy. The original seedling of Karmijn de Sonnaville is now 29 years old.

The variation might be explained by juvenility. Since about 1970, many shoots have been taken from the original seedling for budding and grafting. Some of these shoots might be in the juvenile phase and this might be responsible for the variability observed.