Genus-specific host range of Phomopsisamaranthicola (Sphaeropsidales), a bioherbicide agent for Amaranthus spp.

Abstract

Phomopsis amaranthicola, a newly described species discovered in Florida, is under development as a biological control agent for weeds belonging to the genus Amaranthus. Host-range testing was performed on the fungus, using the centrifugal phylogenetic scheme, with Amaranthus hybridus as the focal plant. Forty-five accessions of 21 species in the genus Amaranthus were tested for susceptibility to infection by this fungus. Fifty-six plant species outside the genus Amaranthus were also tested. The latter included crops in which the fungus might be used as a bioherbicide, members of genera that are closely related to Amaranthus, and selections of species that have been reported as hosts of other species of the genera Phomopsis or Diaporthe. Phomopsis amaranthicola did not infect any of the plants from outside the genus Amaranthus but was highly pathogenic to several species in the genus Amaranthus. All Amaranthus species tested were infected to varying degrees by P. amaranthicola; the resulting mortality levels were also variable. Thus, P. amaranthicola appears to be host-specific to the members of the genus Amaranthus. The generic level of specificity of this pathogen renders it not only a safe bioherbicide agent but also one that could be used against several weedy Amaranthus species.

Keywords:

• Phomopsis amaranthicola
• bioherbicide
• Amaranthus
• pigweed

Published online 13 October 2005

Published online 13 October 2005

Acknowledgments

The authors thank David Brenner of the North Central Regional Plant Introduction Station in Ames, Iowa for providing seeds of the accessions tested. This research was supported in part by funds provided by Special Grants Tropical Agriculture, Caribbean Basin Administrative Group (CBAG), USDA Contract No. 94-34135-0649 and USDA-CSREES Special Grants in IPM, No. 97-34365-5001 to R. Charudattan, the University of Florida and USDA, ARS.

Notes

Published online 13 October 2005