Abstract
Research Highlights: Two genets of Armillaria altimontana Brazee, B. Ortiz, Banik, and D.L. Lindner and five genets of Armillaria solidipes Peck (as A. ostoyae [Romagnesi] Herink) were identified and spatially mapped within a 16-year-old western white pine (Pinus monticola Doug.) plantation, which demonstrated distinct spatial distribution and interspecific associations. Background and Objectives: A. solidipes and A. altimontana frequently co-occur within inland western regions of the contiguous USA. While A. solidipes is well-known as a virulent primary pathogen that causes root disease on diverse conifers, little has been documented on the impact of A. altimontana or its interaction with A. solidipes on growth, survival, and the Armillaria root disease of conifers. Materials and Methods: In 1971, a provenance planting of P. monticola spanning 0.8 ha was established at the Priest River Experimental Forest in northern Idaho, USA. In 1987, 2076 living or recently dead trees were measured and surveyed for Armillaria spp. to describe the demography and to assess the potential influences of Armillaria spp. on growth, survival, and the Armillaria root disease among the study trees. Results: Among the study trees, 54.9% were associated with Armillaria spp. The genets of A. altimontana and A. solidipes comprised 82.7% and 17.3% of the sampled isolates (n = 1221) from the study plot, respectively. The mapped distributions showed a wide, often noncontiguous, spatial span of individual Armillaria genets. Furthermore, A. solidipes was found to be uncommon in areas dominated by A. altimontana. The trees colonized by A. solidipes were associated with a lower tree growth/survival and a substantially higher incidence of root disease than trees colonized only by A. altimontana or trees with no colonization by Armillaria spp. Conclusions: The results demonstrate that A. altimontana was not harmful to P. monticola within the northern Idaho planting. In addition, the on-site, species-distribution patterns suggest that A. altimontana acts as a long-term, in situ biological control of A. solidipes. The interactions between these two Armillaria species appear critical to understanding the Armillaria root disease in this region.
Highlights
Armillaria root diseases are among the most damaging and broadly distributed root diseases of diverse woody hosts around the world (e.g., [1,2,3])
The tree height, diameter at breast height (DBH), and survival differed significantly (p < 0.001) by Armillaria colonization status (Table 4) with trees colonized only by A. altimontana exhibiting a greater growth and survival in comparison with trees colonized only by A. solidipes, by both Armillaria species, and not associated with Armillaria (Figure 2). These findings support the hypothesis that A. altimontana is typically nonpathogenic or a weak pathogen and further suggest that A. altimontana could perhaps behave as a beneficial symbiont, epiphyte, or both in western white pine under certain conditions
In a 16-year-old western white pine plantation spanning 0.8 ha, we found and characterized two genets of A. altimontana and five genets of A. solidipes that exhibited distinct spatial distribution and interspecific associations
Summary
Armillaria root diseases are among the most damaging and broadly distributed root diseases of diverse woody hosts around the world (e.g., [1,2,3]). Herink) is well-known as a virulent primary pathogen that causes root disease on diverse conifers within the inland western regions of the contiguous USA [4], where A. altimontana Brazee, B. Banik, and D.L. Lindner (formerly North American Biological Species X, NABS X) frequently co-occur [5]. A. altimontana is frequently considered a weak or secondary pathogen [6], little has been documented about its impact on tree health and growth. A. altimontana and A. solidipes are frequently found in association with western white pine (Pinus monticola Doug.) [5]
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