First report of Metarhizium anisopliae infecting queens of Atta cephalotes (Hymenoptera: Formicidae) from Colombia

Abstract

The fungus Metarhizium anisopliae was obtained from two dead queens of the ant species Atta cephalotes collected in Colom­bia. The isolates were grown on PDA, and identified as 136 and 137. Their pathogenicity was evaluated against workers of A. cephalotes and compared with isolates obtained from other insect sources. Mortality and infection of ant workers were monitored for 9 days. Hall infective concentration (C1,₄₁) and half sporulation time (TE_so) was determined by probit analysis. Strains 136, 137, and 77 at the minor dosis 5.4x10' conidia/ ml, presented the lowest TE_so (200.3, 180.7 and 197.7 hours) compared with the other strains that varied in a range of 237.3 to 672.7 hours post-inoculation. The Cl50 after 144 hours post-exposure was 9.93x10⁷conidia/m1 and 4.5x10' conidia/ml for the isolates 136 and 137 in contrast with the isolates 82 and 77 with 7.5x10' conidia/ml and 1.7x10" conidia/ml respectively. Molecular characterization by PCR-RFLP. produce(' a fragment of 1.2 kbp of ADN that digested with restriction enzymes generated a banding pattern in agarose gel that permitted to locate the interest isolates in a group with 60% of similarity among them, accompanied by other three isolates. The evaluation of the ADN by RAPD's generated two groups, in one of them are isolates 136 and 137 with 71% percentage of disagreement, demonstrating high genetic variability between them.