Limiting temperatures for urediniospore germination are low in a systemic rust fungus of tallgrass prairie

Abstract

Potential responses of plant disease phenology to climate change have been addressed primarily in agricultural systems. As a first step toward understanding the phenology of Uropyxis petalostemonis, a rust fungus commonly infecting the legume Dalea candida in USA tallgrass prairie, we evaluated the effects of temperature on urediniospore germination. While urediniospore germination for many rust fungi has been reported to decline only when temperatures are well above 25 C, in vitro germination of U petalostemonis dropped sharply at this temperature. Responses observed on water agar, potato dextrose agar and lima bean agar were similar, although lima bean agar supported a higher percentage germination overall. The low limiting temperatures suggest that most epidemically important new infections by U petalostemonis occur in spring. High summer temperatures in tallgrass prairie might push infection by this rust fungus species to earlier in the year and select for stronger systemic growth characteristics.

• Basidiomycetes
• Dalea candida
• Fabaceae
• phenology
• Uredinales
• Uropyxis petalostemonis

We thank H. Alexander, H. Ahmed, R. Bowden, A. Jumpponen, C. Kramer, F. Trail and anonymous reviewers for helpful comments and J McCain for identification of U. petalostemonis. We thank S. Udomvaraphunt for assistance with a figure. We appreciate the work of the many people who have maintained the KPBS datasets through the years. It also is a pleasure to acknowledge support by the US National Science Foundation under Grants DEB-0130692 and DEB-0516046, by NSF grant EF-0525712 as part of the joint NSF-NIH Ecology of Infectious Disease program and by the NSF Long-Term Ecological Research Program at KPBS. This is contribution 08-98-J of the Kansas State Experiment Station.