The selection of fruit trees rootstocks is a continuous preoccupation of numerous research stations because they permit to modify the growing behavior of the fruit tree. At the end of years 1950 began the decline of the cherry-tree culture in Belgium, bound mainly to the slowness of fruit set, to the high costs of maintenance and picking. Adaptations to modern techniques and to intensive culture were necessary to encourage this culture as diversification source. The control of the excessive tree vigor was the first objective. The selection of dwarfing rootstocks for soft fruit cherry-tree started at the CRA-W around 1960. More of 200 potential rootstocks, all ornamental Prunus, have been tested progressively and characterized . 3 rootstocks were first selected: Inmil (Prunus incisa x serrula), Damil (Prunus dawyckensis) and Camil (Prunus canescens), each presenting different potentialities of growth reduction as well as earliness of flower set and intensity of flowering.
Cherry picking in orchard grafted on Damil®
The objective of this project is to select a rootstock for sweet cherry presenting a (same or near) dwarfing level of the one induced by Damil, cumulated to the earliness of flower/fruit set as wished by producers. In this setting, a population of more than 250 candidates, all issued of cores seedlings (result of a free pollination of Prunus dawyckensis within the conservatory orchard of Gembloux) is tested according to the following selection criterias: - faculty to the vegetative multiplication, - behavior in nursery, - compatibility to the budding, - rate of dwarfing, - technical qualities (anchorage, suckering, resistance to the cold weather, adaptation to conditions of soil, sensitivity to diseaeses,…) - earliness of flowering and fruit set, - quality of the fruit production.
Complementary tests of the 27 candidates must permit to confirm observations concerning the fruit set induced by the precocious flowering (since the 3rd year) and by the high intensity of May clusters initiation. The induced production increase should however guarantee the maintenance of the fruit size. Two candidates will be introduced in international test. Other unexpected observations will be confirmed: they concern the induced modifications by the rootstock on the tree shape of the budded cultivar, on the date of fruit maturity as well as on the fruit size.
More than 120 seedlings have been multiplied vegetatively. Candidates rootstocks have been budded with the varieties of soft cherry " Burlat " and " Lapins " chosen respectively for their weak or important floral induction capacity. These trees have been implanted progressively on three different sites and their behavior of growth, flowering and fruit set has been followed annually. 27 potential candidates presenting a high intensity of May clusters production ( more that the one observed on Damil) since the third and fourth years of plantation have been identified.
Burlat May flower cluster evolution on 2 years old wood in relation to rootstock candidate