First Report of the Pitch Canker Fungus (Fusarium circinatum) in the Sierra Nevada of California.

The pitch canker fungus, Fusarium circinatum (teleomorph Gibberella circinata), was isolated from a branch originating from rootstock of a Douglas-fir (Pseudotsuga menziesii) graft in a breeding orchard at 1,000m elevation in El Dorado County, California. We visited the orchard after the New Zealand Ministry of Agriculture and Forestry reported in November 2003 that a Douglas-fir scion (branch cutting) shipped from there in January-and subsequently grafted and held in a quarantine facility near Christchurch-was infected with the pitch canker fungus. We took samples throughout the orchard of any branches that appeared unhealthy. In addition, asymptomatic branches from the tree alleged to be the source of the New Zealand infestation were collected to assay for propagules of F. circinatum. Wash water from these branches was negative for the pathogen. Likewise, F. circinatum was not recovered from water washings of 20 branches collected randomly throughout the orchard. Fifteen branch samples collected from symptomatic Douglas-fir grafts were cultured on water agar and only one yielded a colony with an appearance consistent with F. circinatum. A single spore subculture of this isolate was confirmed as F. circinatum on the basis of colony morphology and the structure of the microconidiophores (1). The virulence of this isolate was evaluated by inoculating susceptible 2-year-old Monterey pine (Pinus radiata) seedlings with a toothpick to wound the main stem and insert potato dextrose agar colonized by the fungus. Twenty-four days later, pitching and yellow needles were evident at the site of inoculation, and removal of the bark revealed resin-soaked and discolored tissue. Concurrent with the pathogenicity test described above, a culture of the putative F. circinatum isolated in New Zealand was inoculated into Monterey pines with an identical outcome. The fungus was reisolated from lesions from both sets of inoculations and confirmed as F. circinatum based on morphological criteria. Isolates GL285 and GL286 are available from T. R. Gordon upon request. Prior to its discovery in the Sierra Nevada, pitch canker in California was known only from counties on or near the coast. Our report indicates the pathogen can survive and infect trees 110 km east of the previous most-inland site of infestation. It remains to be seen how extensively pitch canker will develop in the Sierra Nevada. Douglas-fir is only moderately susceptible to F. circinatum, which has not been observed to cause significant damage to this species. On the other hand, low-elevation Sierra Nevada pines including P. sabiniana, P. coulteri, and P. ponderosa are substantially more susceptible than are Douglas-fir in greenhouse tests (2). References: (1) T. R. Gordon et al. Mycol. Res. 100:850, 1996. (2) T. R. Gordon et al. Plant Dis. 85:1128, 2001.

First Report of the White Pine Blister Rust Fungus (Cronartium ribicola) Infecting Whitebark Pine (Pinus albicaulis) and Ribes spp. in the Jarbidge Mountains of Northeastern Nevada.

The Jarbidge Mountains are a remote and little-visited desert mountain range at the northern edge of the Great Basin in Elko County, NV, 110 km north of Elko and 115 km southwest of Twin Falls, ID. The forest is dominated by subalpine fir (Abies lasiocarpa) at lower elevations and whitebark pine (Pinus albicaulis) at higher elevations; limber pine (P. flexilis) occurs along streams in canyons at lower elevations (2). P. albicaulis and P. flexilis are hosts for the blister rust fungus, Cronartium ribicola. In the late 1990s, a survey across the Intermountain West reported no evidence of C. ribicola in the Jarbidge Mountains or elsewhere in the central Great Basin (3). However, unpublished observations by D. A. Charlet in 1988 and 2001 indicate that blister rust has been present in the Jarbidge Mountains for at least 16 years. In September 2002, D. R. Vogler visited the Jarbidge Mountains over a 2-week period, examining whitebark pines along the unpaved route through the Humboldt-Toiyabe National Forest connecting Highway 225 and Jarbidge, NV. Blister rust-infected whitebark were found in two locations: (i) Coon Creek Summit (2,575 m elevation), atop the divide between the Great Basin to the south and the Columbia Plateau to the north, and (ii) Bear Creek drainage (2,315 to 2,405 m elevation), 6.7 km northeast of Coon Creek Summit. At Coon Creek Summit, three whitebark pines ranging in diameter from 10 to 30 cm at breast height (dbh) were infected (evidenced by spindle-shaped branch swellings, aecia, and aeciospores), with the oldest infection occurring on wood produced in 1975. Assuming a mean needle retention of 10 years, the first pine infection likely occurred between 1975 and 1984. Ribes montigenum and an unknown Ribes sp. were common at Coon Creek Summit but were not infected. In the Bear Creek drainage north of the divide, 27 whitebark pines ranging in size from under 0.3 m high to 12 cm dbh were found infected, with the oldest infection on 1976 wood indicating an origin between 1976 and 1985. Most pines there, however, appeared to have been infected between 1994 and 1998. At Bear Creek, infection on Ribes spp. was common, with R. cereum the most frequently infected species. Voucher specimens of R. cereum (KPK-948 and KPK-949) are archived in the fungal herbarium at the Institute of Forest Genetics, Placerville, CA. On pine, fresh spermatia and aeciospores were abundant even though it was late in the season. Late sporulation has also been observed above 2,500 m on western white (P. monticola) and whitebark pine northeast of Lake Tahoe in Nevada (4). To our knowledge, our report marks the first recorded intrusion by C. ribicola into the north-central Great Basin. Recently, the first report of C. ribicola on Rocky Mountain bristlecone pine (P. aristata) was documented in southern Colorado (1). Now, Great Basin bristlecone (P. longaeva), which is restricted in Nevada to higher elevations in the eastern and southern parts of the state (2), may also be at risk; the northernmost occurrence of this last whitepine holdout from blister rust is in the Ruby Mountains, 135 km south of our findings in the Jarbidge Mountains. References: (1) J. T. Blodgett and K. F. Sullivan. Plant Dis. 88:311, 2004. (2) D. A. Charlet. Atlas of Nevada Conifers. University of Nevada Press, Reno, 1996. (3) J. P. Smith and J. T. Hoffman. Western North American Naturalist 60:165, 2000. (4) J. P. Smith et al. Plant Dis. 84:594. 2000.

Ectomycorrhizal specificity patterns in a mixed Pinus contorta and Picea engelmannii forest in Yellowstone National Park.

We used molecular genetic methods to test two hypotheses, (i) that host plant specificity among ectomycorrhizal fungi would be common in a closed-canopy, mixed Pinus contorta-Picea engelmannii forest in Yellowstone National Park and (ii) that specificity would be more common in the early successional tree species, P. contorta, than in the invader, P. engelmannii. We identified 28 ectomycorrhizal fungal species collected from 27 soil cores. The proportion of P. engelmannii to P. contorta ectomycorrhizae was nearly equal (52 and 48%, respectively). Of the 28 fungal species, 18 composed greater than 95% of the fungal community. No species was associated exclusively with P. contorta, but four species, each found in only one core, and one species found in two cores were associated exclusively with P. engelmannii. These fungi composed less than 5% of the total ectomycorrhizae. Thus, neither hypothesis was supported, and hypothesized benefits of ectomycorrhizal specificity to both trees and fungi probably do not exist in this system.

A 5.8S nuclear ribosomal RNA gene sequence database: applications to ecology and evolution.

We complied a 5.8S nuclear ribosomal gene sequence database for animals, plants, and fungi using both newly generated and GenBank sequences. We demonstrate the utility of this database as an internal check to determine whether the target organism and not a contaminant has been sequenced, as a diagnostic tool for ecologists and evolutionary biologists to determine the placement of asexual fungi within larger taxonomic groups, and as a tool to help identify fungi that form ectomycorrhizae.