DIVERSITY AMONG ISOLATES OF VERTICILLIUM-LECANII AS EXPRESSED BY DNA POLYMORPHISM AND VIRULENCE TOWARDS BEMISIA-TABACI

Thirty-six isolates of Verticillium lecanii and Verticillium sp. were taken from different hosts (both insects and rusts) and geographical l ocations. The isolates were analyzed for genomic variability, as expre ssed by random amplified polymorphic DNA (RAPD), in relation to virule nce on Bemisia tabaci. Virulence on larvae of B. tabaci within these i solates ranged from 0% to 83%. RAPD analysis was performed employing t wo different arbitrary decamer primers and the calculated similarity c oefficients were subjected to cluster analysis using the unweighted av erage linkage (UPGMA) algorithm. The dendrograms obtained with each of the two primers were identical. Eight cluster groups and three unclus tered isolates were obtained by selecting a similarity level of 80%. T he amplification pattern of DNA obtained by RAPD for the various isola tes suggested that V. lecanii is a highly diverse species. No correlat ion could be established between virulence and either RAPD polymorphis m of the fungal isolates or the insect host from which they were isola ted. Generally, no correlation could be established between the cluste ring of V. lecanii strain and geographical location although a limited number of strains obtained from Russia and Georgia were assembled in the same cluster and those from Kazakhstan were clonal.