Impact of the Crown Gall Disease on Vigour and Yield of Rose Trees

Authors: C. Poncet, C. Antonini, A. Bettachini, D. Hericher, S. Pionnat, L. Simonini, Y. Dessaux, X. Nesme
Abstract:
Crown gall is a widespread plant tumor disease in temperate regions of the world caused by virulent strains of Agrobacterium (Smith & Townsend, 1907) Conn. This bacterium is a common soil pathogen that can attack 93 plant families. Nevertheless, opinions on the incidence of the disease are very divergent. In the case of roses, French growers consider crown gall to be the principal disease in nurseries: 20 percent of the stock is infected every year and cannot be sold but the direct effect of crown gall on the yield of rose trees remains a much debated issue. However, an important increase in the frequency of crown gall in greenhouses has been noticed, related to the use of a new propagation method named stenting. In order to evaluate the effect of the disease on the vigour of rose trees, a representative affected plantation has been analysed. 18 months after planting, a 63% difference of stem diameter between healthy and affected plants was observed. Furthermore, a plot was set up at INRA Antibes to quantify the effect of crown gall on nursery stock and on the yield of rose trees after artificial inoculation during grafting. The mortality rates of contaminated and control plants during the growing phase were 5.5% and 0.6%, respectively. Plant performances were studied for 8 months in the greenhouse. The controls produced a mean of 9.7 flowers per plant while contaminated plants produced only 6.2 flowers during the same period.

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