STUDY OF THE BEHAVIOUR OF PRUNUS CULTIVARS TOWARDS AGROBACTERIUM RADIOBACTER VAR. TUMEFACIENS.

ISHS Acta Horticulturae 283: IV International Symposium on Plum and Prune Genetics, Breeding and Pomology

**STUDY OF THE BEHAVIOUR OF PRUNUS CULTIVARS TOWARDS AGROBACTERIUM RADIOBACTER VAR. TUMEFACIENS.**

Authors:

A. PIERRONNET, V. ESCALETTES

Abstract:
A. tumefaciens is a telluric bacterium which causes heavy losses in the Prunus rootstocks by inducing crown-gall. No chemical pesticide is efficient against this bacterium which multiplies in injured tissues causing a gall, which can occur every time during the plant's life. If the K84 strain of A. radiobacter can be used to protect plants against A. tumefaciens more or less successfully, it may be possible to use genetic resistance by exploiting the variability in the genus Prunus as an alternative approach.

In order to evaluate this variability, the development of an early test which is also rapid and efficient has been undertaken.

Two methods have been compared :

Woody cuttings test: Cuttings of different Prunus and of interspecific hybrids, inoculated at the base with an aggressive strain of A.tumefaciens were placed under favourable conditions for rooting. After three months the increase for the size grafts was measured by calculating diameter of the gall minus diameter of the cutting. A classification of the cultivars according to their susceptibility was established and compared to that obtained under the natural orchard conditions.
In vitro test : Prunus cultivars or hybrids were multiplicated and elongated through in vitro culture. One month after inoculation on the shoots after being cut at the top, the diameter of the developed gall is correlated with the level of susceptibility established with the other methods.

The reliability of the two methods is discussed and the first results concerning rootstocks susceptibility are presented.

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