Genotypic Properties of the Entomopathogenic Fungus Nomuraea rileyi

The dimorphic entomopathogenic fungus Nomuraea rileyi, an important biological control agent of various noctuid defoliators, is known to regulate Anticarsia gemmatalis, the key soybean pest in South America and the southeastern United States. At present, very little is known about the isolates that are associated with the endemic or epizootic phases of this disease agent. The development of molecular markers capable of delineating N. rileyi pathotypes is essential for such an analysis. In this study, various molecular techniques, including internal transcribed spacer (ITS) sequence analysis, randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and telomeric fingerprinting methods, were employed to identify genotypes. Analysis of the ITS-5.8s and 28s regions of N. rileyi isolates suggested that this species was more closely related to Metarhizium anisopliae and M. flavoviride than to Nomuraea atypicola andN. anemonoides. These findings and comparisons with other studies suggest that the systematics of the genus Nomuraea needs reexamination. Analysis of the telomeric fingerprinting, RAPD, and AFLP data produced very similar associations among different Nomuraea. In all cases, the non-rileyi isolates (N. anemonoides and N. atypicola) appeared unrelated to the N. rileyi. The N. rileyi isolates, mainly isolated from A. gemmatalis, were grouped into two clusters: one contained the Florida isolates and the other consisted of a diffuse group of South American isolates. Calculated genetic distances among the different N. rileyi isolates corresponded to geographical isolation.