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Ecology and Epidemiology

Temperature Effects on Basidiospore Germination and on Infection of Slash Pine Seedlings by Cronartium quercuum f. sp. fusiforme. E. George Kuhlman, Research plant pathologist, Southeastern Forest Experiment Station, U.S. Department of Agriculture, Forest Service, 320 Green Street, Athens, GA 30602; William D. Pepper, station biometrician, Southeastern Forest Experiment Station, U.S. Department of Agriculture, Forest Service, 320 Green Street, Athens, GA 30602. Phytopathology 84:735-739. Accepted for publication 28 April 1994. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994. DOI: 10.1094/Phyto-84-735.

In vitro germination of basidiospores of 10 isolates of Cronartium quercuum f. sp. fusiforme occurred within 24 h at temperatures of 832 C. At 32 C, only very short germ tubes developed. Germination was frequent at temperatures of 1228 C, and 90% of the maximum germination occurred at 14.629.6 C. On the basis of second-degree polynomial regressions, the optimum temperatures during 24 h of moist incubation for the infection of pines were 17.7 and 19 C in two experiments. Moist incubation for 24 h at 11.623.4 C resulted in ≥ 90% of the maximum infection rate for susceptible slash pine seedlings. Basidiospores were able to initiate infections over a broad temperature range of 828 C during a 24-h period of moist incubation. The shape and height of curves for germination of each rust isolate or infection of each pine family did not differ significantly, indicating neither factor interacted with temperature.

Additional keywords: fusiform rust, Pinus elliottii.