PATHOTYPE VARIATION OF THE REPRESENTATIVE GENOTYPES OF ASCOCHYTA RABIEI IN THE BEJA REGION
R. Salah, S. Hamza, S. Samir, A. Rebai, , G. Kahl, H. Moncef
Seventeen representative genotypes of Ascochyta rabiei in the Beja region were analyzed for virulence variation. Virulence characterization was based on rating Ascochyta blight disease on eight differential cultivars using the Riahi et al. (1990) scale. Cluster analysis of the virulence revealed five highly virulent phenotypes because at least six of the differential lines were severely infected. Virulence cluster analysis was compared to phylogenetic grouping as determined by Morjane et al. (1997) using RFLP assay with microsatellite probes. The correlation coefficient between the virulence and RFLP similarity matrices was low (0.02). This low association indicates that DNA polymorphism is independent of virulence because of virulence instability in Tunisia probably due to the utilization of non resistant cultivars and the occurrence of sexual reproduction between the isolates.