Abstract

This project provides evidence that there are two distinct species of Aschersonia fungi that kill pest whiteflies: One in the New World and one in the Old World.

Issue

The controversy involves a fungus used for biological control of whiteflies (insects that attack plants and spread viruses). For many years a group of similar-looking fungi with orange spores have confused biologists. Morphological data could not easily distinguish whether the orange-spored fungi represented one species or two. If there is more than one species, then foreign-collected fungi should not be introduced into the United States for fear of introducing an organism that could displace native species.

Response

We used genetic information to distinguish two species among the orange-spored fungi that attack whiteflies. Based on phylogenetic analysis of sequence data from four different genes, we found that there are two distinct species: Aschersonia placenta, which occurs in Europe, Asia, and Africa; and Aschersonia aleyrodis, which occurs in North and South America. The two species evidently diverged following a dispersal event many thousands of years ago. After our genetic analyses, we examined many specimens to seek corroborating morphological characters and reject those that are so variable as to be misleading. As a result we can now reliably distinguish the two species using either genetic or morphological data.

Impact

Our ability to distinguish two similar species that attack whiteflies improves our understanding of the natural resource base that can support American agriculture. Efforts to develop these fungi as whitefly biological controls can now proceed relative to the information that Old World cultures represent a different species. This has an important regulatory impact: a non-native species should not be introduced to this country lightly. We suggest that only the native species be explored as a biological control of whiteflies in U.S. greenhouses and on field crops.

Funding Sources

• Other Federal non-USDA (e.g., NSF, NIH, DOA, DOD)

Key Personnel

• Miao Liu, PhD candidate, Department of Plant Pathology, Cornell University