36th International Carrot Conference Abstract

INTEREST OF A SEMI-CONTROLLED TEST FOR SCREENING CARROT RESISTANCE TO RHIZOCTONIA SOLANI

F. Villeneuve^(1)*, F. Latour⁽¹⁾, F. Pascaud⁽¹⁾, E. Geoffriau(2)

Ctifl centre de Lanxade, 28 toute des Nébouts, 24130 Prigonrieux, France

AGROCAMPUS OUEST, IRHS UMR 1345 INRA-ACO-UA, 2, rue André Le Nôtre, 49045 Angers Cedex 01, France

* Corresponding author

With the development of carrot cultures in the South West of France since 1990’, Rhizoctonia solani has become one of the most damaging fungal pathogens in carrot crops in France. Its prevalence and widespread implication in several symptoms: damping-off, receding collars, crater rots, crown rots and forking were demonstrated. Isolates of AG 2-2 IIB are known to cause the most common symptoms: crater rot (Villeneuve and al., 2009). In France, the disease control of R. solani in carrot with fungicides is not yet feasible because no agent is registered. Furthermore, the non-chemical controls like antagonists are not yet available for agricultural practices. On the other hand, we observe some differences of varietal sensibility in field, especially for the crater rots symptoms. Breeding for R. solani resistance has been difficult mainly because of the lake of identified resistance donors in cultivated varieties including local accessions, landraces different species of Daucus. Screening under field conditions is only possible in fields with a high inoculum pressure. However, it is difficult to ensure homogeneous spatial and temporal distribution of the inoculum. The presence of other pathogens and environmental variation can moreover introduce unforeseen complexity into data interpretation. So we have developed a method for screening for resistance in semi controlled conditions. It’s little representative of commercial growth conditions but they allow the amount and distribution of inoculum to be controlled and limit other sources of variation. Different parameters have been studied like: inoculum quantity, stage of carrot development, relation between damping-off damages and crater rot damages, different varieties, Daucus species and progenies. The proposed test seems to be sufficient reproducible year after year and robust to identify the differences in the varietal resistance.

Last updated Thursday, 25-Jul-2013 11:52:21 CDT