Mexican Strains of Hirsutella Isolated from Diaphorina citri (Hemiptera: Liviidae): Morphologic and Molecular Characterization

Diaphorina citri Kuwayama (Hemiptera: Liviidae), the vector of huanglongbing, has been found in several citrus areas of Mexico, apparently attacked by the fungus Hirsutella citriformis Speare (Hypocreales: Ophiocordycipitaceae). As this entomopathogen could represent a potential agent of D. citri biological control in the country, we performed this study to characterize 7 strains of the fungus isolated from this insect. For the molecular characterization we used internal transcribed spacer sequences 1 and 2 (ITSs 1 and 2) and 28S rDNA. In the morphological description we determined size of reproductive structures in the strains as well as their blastospore production capacity. BLAST analysis of the ITSs sequences showed less than 91% and 72% of identity and coverage with Ophiocordyceps sinensis or H. citriformis; meanwhile, gen 28S sequences showed high identity (98–99%) and coverage (98–100%) with O. elongata (Petch) G.H. Sung, J.M. Sung, Hywel-Jones & Spatafora and O. coccidiicola (Kobayasi) G.H. Sung, J.M. Sung, Hywel-Jones & Spatafora. The phylogenetic analysis using 28S sequences demonstrated that the Mexican strains are closely related with H. citriformis; however, size of phialide and conidial diameter showed differences with dimensions reported for the species in the original description. Under dark conditions, 6 strains were able to produce mucilaginous colonies that contained blastospores; these structures caused 30.8–41.2% mortality in the target insect. The results suggest that Hirsutella strains isolated from D. citri in Mexico, correspond to H. citriformis. We found dimorphic capacity and variability in size of the reproductive structures of the fungus. This is the first report of ITSs and 28S sequences of H. citriformis obtained from strains isolated from D. citri.