摘要：Macrophomina phaseolina is a fungus which affects more than 300 cultivated species. It is one of the most important biotic stresses on sesame (Sesamum indicum L.). A successful control strategy, especially plant resistance management, depends on comprehensive knowledge about genetic variability for both fungus and plant. To evaluate genetic diversity of M. phaseolina affecting sesame in the most important crop production region of Venezuela, seven isolates were characterized by means of phenotypic traits, and RAPD markers. Four of these isolates were used for evaluating the interaction with four sesame genotypes in two ways: interaction in vivo by inoculation, and effect of root and stem extracts on fungus growth. Variability for growth velocity (optical density ranged between 1.69 to 2.32 at 96 hours of growing) (P≤0.05) and microsclerotia production (18-56 in 100 μL) (P≤0.05), was observed. Ten primers used were able to amplify the DNA, generating 81 bands (100% polymorphic). Ordination of the seven isolates by means of principal coordinates analysis based on RAPD did not show a consistent relationship with phenotypic attributes or geographical origin. After inoculation, length lesion produced by the four isolates did not show statistical differences, but germination percentage did (P≤0.01). One of the fungus isolates reduced up to almost 70% average germination of the four sesame genotypes. Mycelial growth of four isolates was inhibited in 17-32 % as compared to the control. These results indicate it is difficult to manage charcoal rot by means of obtaining resistant cultivars because of the fungus variability found in all the levels evaluated..
