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Aims:  The genetic diversity of Beauveria bassiana was investigated by comparing isolates of this species to each other (49 from different geographical regions of Brazil and 4 from USA) and to other Beauveria spp. Methods and Results:  The isolates were examined by multilocus enzyme electrophoresis (MLEE), amplified fragment length polymorphism (AFLP), and rDNA sequencing. MLEE and AFLP revealed considerable genetic variability among B. bassiana isolates. Several isolates from South and Southeast Brazil had high similarity coefficients, providing evidence of at least one population with clonal structure. There were clear genomic differences between most Brazilian and USA B. bassiana isolates. A Mantel test using data generated by AFLP provided evidence that greater geographical distances were associated with higher genetic distances. AFLP and rDNA sequencing demonstrated notable genotypic variation between B. bassiana and other Beauveria spp. Conclusion:  Geographical distance between populations apparently is an important factor influencing genotypic variability among B. bassiana populations in Brazil. Significance and Impact of the Study:  This study characterized many B. bassiana isolates. The results indicate that certain Brazilian isolates are considerably different from others and possibly should be regarded as separate species from B. bassiana sensu latu. The information on genetic variation among the Brazilian isolates, therefore, will be important to comprehending the population structure of B. bassiana in Brazil.

Fifty isolates of Beauveria bassiana (Balsamo) Vuillemin, 1912 (Ascomycota: Clavicipitaceae) were analyzed by morphology, for their pathogenic potential to Boophilus microplus (Canestrini, 1887) (Acari: Ixodidae) larvae, and by Random Amplified Polymorphic DNA-Polymerase Chain Reaction technique. Morphological analysis demonstrated that isolates present characteristics compatible to those described for B. bassiana in the literature. Virulence test demonstrated that all isolates present lethal effect on larvae and that the lethal concentration varies among isolates. The most virulent isolate was the only one obtained from human infection, which was also the only isolate presenting synnemata. The study on genetic variability among the isolates allowed the identification of 23 electrophoretic profiles. The established groupings suggest that most of the isolates obtained from B. microplus of the same locality present low genetic variation. In this way, the data in the present study will contribute to a meticulous characterization of these B. bassiana isolates.

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The use of entomopathogenic fungi to control arthropods has been reported worldwide for decades. The aim of the present study was to evaluate the virulence of 30 Metarhizium anisopliae s.l. Brazilian isolates from different geographical regions, hosts or substrates on the larvae of Rhipicephalus (Boophilus) microplus ticks under in vitro conditions to the selection of virulent isolates in order to be further used in biological control programs. The current study confirmed the lethal action of M. anisopliae s.l. isolates on R. (B.) microplus larvae with different mortality levels, usually directly proportional to the conidia concentration. No relationship was found between the origin of the isolate and its virulence potential or between the virulence potential and conidia production. Three isolates (CG 37, CG 384 and IBCB 481) caused a high percentage of larval mortality, reaching LC(50) at 10(6) conidia ml(-1), thus requiring a lower conidia concentration to cause an approximately 100% larval mortality. The results of this study suggest that these three isolates are the most promising for use in programs aimed at microbial control in the field.

The purpose of this work was to evaluate the in vitro virulence of three isolates of Beauveria bassiana to eggs and larvae of the tick Boophilus microplus. The fungus tested were isolated from engorged females of B. microplus collected on the field, and identified as Bb28, Bb29 and Bb30. These isolates were evaluated by immersion of eggs and larvae in suspensions with different conidial concentrations: 10(8), 10(7), 10(6) and 10(5) conidia/ml and compared to the control groups. In the treated eggs, there was a percentage much smaller of hatching than that observed in the controls. The egg hatch was inversely proportional to the conidial concentration. In larval bioassays, all isolates resulted in a higher mortality of larvae compared to the control according to the conidial concentrations/ml, 10 days after treatment inoculation.