AFLP analysis of the entomopathogen Nomuraea rileyi

The dimorphic, asexual entomopathogen Nomuraea rileyi is a well known morta lity agent of noctuid insects in subtropical and temperate agricultural sys tems. Genomic DNA was extracted from N. rileyi isolates collected from Anti carsia gemmatalis velvetbean caterpillar in Florida, Brazil, and Argentina as well as from non-Anticarsia hosts and subjected to a modified single-ste p AFLP analysis. Compared to RAPDs, the employed AFLP method provided a rel iable and sensitive method for detecting genomic differences among N. riley i 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 polym orphic and ranged 400-3000 bp. A total of 43 haplotypes were found among th e 73 N. rileyi isolates. Analysis of the AFLP data revealed extensive polym orphism among different N. rileyi isolates derived from both homologous and heterologous noctuid host species. For example, the dominant haplotype iso lated from the Florida A. gemmatalis population was detected in diseased Ps eudoplusia includens soybean looper and Plathypena scabra green cloverworm. Cluster analysis demonstrated that the AFLP polymorphisms observed among t he N. rileyi isolates were associated with geographical location and/or wit h local insect population(s). Examination of this entomopathogen from a sin gle field over a multiseasonal time frame demonstrated that the N. rileyi p opulation is stable and can probably overwinter and initiate the disease cy cle the following year.