ARS Collection of Entomopathogenic Fungal Cultures

By Richard A. Humber

Location

U.S. Department of Agriculture, Agricultural Research Service, U.S. Plant, Soil, and Nutrition Laboratory, Tower Road, Ithaca, NY 14853-2901

Loans

Cultures are distributed to recognized institutions and scientists

Associated
libraries

2,000 books, journals, and reprints; across the street from the E.A. Steinhaus collection of more than 10,000 reprints on invertebrate pathogens and pathology

Number of
accessions

5,500 isolates; ca. 375 fungal species from 900 hosts

Types

Few in associated herbarium facility

Curator

Richard A. Humber
Phone: (607) 255-1276, fax: (607) 255-1132
e-mail

Home page

Background

The Agricultural Research Service Collection of Entomopathogenic Fungi (ARSEF) was established to provide fundamental support for basic and applied research on the fungal pathogens of invertebrates. Since its inception in the early 1970's, this collection has served as a general research resource for the isolation, collection, preservation, and distribution of fungi isolated primarily as pathogens from insects, other arthropods, and nematodes. Emphasis has always been placed on acquiring and distributing strains under active study for use as potential biological control agents, but the collection is increasingly being used as a source of fungal compounds having potential uses in pest control and medicine. Basic research associated with the collection includes fungal systematics, fungal cytology, pathobiology, and methodology for fungal cryopreservation. The culture collection and its associated collection of specimens, microscope slides, and photographic images provide invaluable support for taxonomic research on the fungal pathogens of invertebrates and the identification of these pathogens.

ARSEF was begun by Dr. Richard S. Soper as a research collection at the ARS Plant, Soil, and Water Laboratory at the University of Maine in Orono. The original prefix used to identify the collection was UMO (for its location on the University of Maine campus) and was later changed to the site-independent prefix RS (for Richard Soper). In 1985, the collection became known as ARSEF when the collection was registered with the World Data Center on Microorganisms. In 1978, the ARS Insect Pathology Research Unit (R. Soper, research leader) and its culture collection were relocated from Maine to the Cornell University campus and into facilities in the newly constructed Boyce Thompson Institute (BTI). This ARS unit, the name of which was later changed to the Plant Protection Research Unit (PPRU) in October 1985 after it merged with several small ARS units on the Cornell campus, was closely integrated with BTI's biological control program for 11 years. After occupying transitional quarters outside BTI in 1989 and 1990, the PPRU insect pathology program and the culture collection moved in November 1990 into renovated laboratory space in the U.S. Plant, Soil, and Nutrition Laboratory.

PPRU maintains and operates the ARSEF culture collection; this collection has never been owned or controlled by BTI, despite its long and close association with BTI. This culture collection is one of the largest microbial germplasm collections in USDA-ARS and is widely recognized for its active support and encouragement of global research on fungal pathogens of arthropods. There is a small herbarium associated with the collection for specimens and microscope slides. The collection acquired digital imaging capabilities for both stereo and compound microscopes in 1994 and is now accumulating an archive of digital images of entomopathogenic fungi.

Since 1977, all strains in the collection have been stored by immersion in liquid nitrogen at -196 °C, but limited cryogenic storage capacity will require many strains to eventually be shifted from cryogenic to lyophil storage. Requests for cultures are filled with either live cultures on appropriate solid or liquid media or lyophil tubes (plus instructions for fungal recovery).

Identification
Service

Specimens and cultures of unidentified fungi from invertebrates can be submitted to the ARSEF curator for diagnosis. This service is an important function of the collection and is provided without charge for small numbers of specimens. Identifications and information about the status of specimens are mailed to the sender.

Databases

The ARSEF collection is managed with a customized database management application that tracks all information about accessions, storage of isolates, and requests for cultures. The software also generates forms guiding the selection and tracking of requested isolates, confirmations of cataloging information for depositions, and various reports, including fully formatted, indexed catalogs of the ARSEF collection.

Basic accession information about many ARSEF strains is available online through the Microbial Germplasm Database. Alternatively, isolate accession data will also be available on the World Wide Web through the PPRU home page .

Research

The research focus of the ARSEF collection is on the systematics, taxonomy, developmental biology, and germplasm preservation for fungal pathogens of insects, mites, spiders, nematodes, and other invertebrates. Past and current research efforts have emphasized (1) the specific, generic, and familial systematics of the Entomophthorales (Zygomycetes), particularly on resolving the complexes of Entomophaga species affecting lepidopteran and orthopteran hosts (fig. 6) and molecular characterization of species such as Zoophthora radicans (fig. 7) to track the establishment and dispersal in the field, (2) the systematics of Metarhizium species, (3) the clarification of the taxonomy of Verticillium lecanii, an important entomopathogen that appears to be a globally distributed species complex, and (4) the discovery and documentation of linkages between conidial (hyphomycete) and the ascomycetous sexual states of fungal entomopathogens such as the species of Cordyceps (fig. 8).

Figure 6. Grasshopper killed
by a complex of Entomophaga
species, which are distinguished by
the types of spores formed, hosts,
geographical ranges, and molecular
and morphological characteristics

Figure 7. Leafhopper infected by Zoophthora
radicans, an effective natural biocontrol agent.
The establishment and dispersal of Serbian
isolates of this species introduced against potato
leafhopper in New York State was confirmed
by molecular systematics techniques.

Figure 8. Cultures of this Cordyceps
species, an ascomycete pathogen of a
cicada, yield only a Paecilomyces
conidial state. Connecting the conidial
and sexual forms of insect-pathogenic
fungi is essential to clarify the systematics
of these fungi and to increase their utility
for biological control.

Selected
Achievements

Observed nuclear events in resting spores, which clarified the life history of fungi in the Entomophthorales