ALTERNATIVE TO MYROBOLAN ROOTSTOCK FOR APRICOT CULTIVATION

The choice of apricot rootstock is first determined by the soil conditions; the adaptation to particular soil conditions being crucial for tree survival.
Additionally, growers could be interested in low-vigour rootstocks for better vigour control and fruit quality.
In Switzerland, apricots are traditionally cultivated on Myrobolan, which is too vigorous for high soil fertility and, thus, not adapted for high-density planting.
Therefore, an enlarged vigour range is needed in order to produce high quality fruits.
The aim of this study was to assess the influence of different rootstocks on survival and agronomic performances of the cultivar Luizet.
A trial with ten different rootstocks was carried out in 1992 in the conditions of central Valais (Switzerland). Trees were traditionally trained as free-standing multiple leader (5.0 m x 3.5 m; 571 trees/ha). The rootstocks were selected according to their compatibility with light-sandy soil, slightly limestone (pH 7.6) and to cover the largest vigour range.
From the 3rd to the 12th year, vigour evolution (trunk cross-area), productivity, yield as well as fruit size were determined.
Citation, Rubira and Jaspi showed a vigour reduction of 35 to 45% compared to Myrobolan, while GF655-2, W61, Pixy and Torinel showed a decrease of 15 to 25%. GF43 and Myrabolan were of similar vigour and Julior showed a 20% higher vigour.

The productivity was increased by 30% for Citation and reduced by 3%, 4% and 33% for Jaspi, Torinel and Julior, respectively.
These four rootstocks induced a better fruit weight compared to Myrobolan.
High decline rate has been observed with GF655-2, W 61, Pixy and Rubira; therefore, these selections cannot be recommended in our conditions.
On the contrary, Citation is promising where densification requires dwarfing rootstocks.
Torinel is a good alternative to traditional Myrobolan, inducing a slight vigour reduction and better fruit size, and Julior could be useful where hillside situation or poor soil fertility require stronger vigour.