AFLP analysis of the entomopathogen Nomuraea rileyi

The dimorphic, asexual entomopathogen Nomuraea rileyi is a well known mortality agent of noctuid insects in subtropical and temperate agricultural systems. Genomic DNA was extracted from N. rileyi isolates collected from Anticarsia gemmatalis velvetbean caterpillar in Florida, Brazil, and Argentina as well as from non-Anticarsia hosts and subjected to a modified single-step AFLP analysis. Compared to RAPDs, the employed AFLP method provided a reliable and sensitive method for detecting genomic differences among N. rileyi populations. All ten AFLP primers produced polymorphic bands when used to amplify the different Nomuraea DNA samples. Approximately 65% (141 bands) of the total scorable bands (216) detected with ethidium bromide were polymorphic and ranged 400-3000 bp. A total of 43 haplotypes were found among the 73 N. rileyi isolates. Analysis of the AFLP data revealed extensive polymorphism among different N. rileyi isolates derived from both homologous and heterologous noctuid host species. For example, the dominant haplotype isolated from the Florida A. gemmatalis population was detected in diseased Pseudoplusia includens soybean looper and Plathypena scabra green cloverworm. Cluster analysis demonstrated that the AFLP polymorphisms observed among the N. rileyi isolates were associated with geographical location and/or with local insect population(s). Examination of this entomopathogen from a single field over a multiseasonal time frame demonstrated that the N. rileyi population is stable and can probably overwinter and initiate the disease cycle the following year.