Articles
INFLUENCE OF ROOTSTOCK AND THE HEIGHT OF GRAFTING ON THE SUSCEPTIBILITY OF APRICOT CULTIVARS TO BACTERIAL CANKER
Some of the factors involved are well known such as frost intensity, hydration of the tissues and the period of inoculation, even if they cannot be kept under control.
The objective of our study was to highlight the influence of two technical practices, rootstock choice and height of the grafting point, on the induced susceptibility of the tree.
The cumulative effect of the rootstock type and the height of the grafting point (modern method: at the soil level (0.3 meter), old method (1.4 meter) on the severity of bacterial canker damages were observed during four years in two different orchards, on the cultivar "Bergeron" grafted on six different rootstocks.
An artificial inoculation was conducted twice during the spring (on one and two-year-old trees) by spraying with suspensions of Ps. syringae pv. syringae and Ps. viridiflava.
A highly significant effect has been observed on both factors studied:
- rootstock effect: apricot seedlings showed their non-adaptation to the given soil conditions (lower growth, higher susceptibility to die-back) whereas peach rootstock and P. mariana induced a higher vigor of the plants and to a lesser extend P. myrobolan seemed to reduce the severity of the symptoms on the grafted variety.
- height of the grafting point: the grafted plants with a crown between 1.8 and 2.5 meter high were more resistant to the disease than the plant grafted at soil level.
A positive interaction between both factors on the induced plant resistance has been observed.
These results must be checked in other conditions of cultivation before they can be generalized.