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Changes in soil microbial communities associated with Armillaria root disease of western white pine (Pinus monticola)

Bradley M. Lalande: Colorado State University

<div>In forests, soil interactions among <em>Armillaria </em>species, microbial communities, and roots may influence tree growth and survival. Two fungal species, <em>A. solidipes</em> (highly virulent) and <em>A. altimontana</em> (less virulent), frequently co-occur in forests of inland northwestern USA. Understanding microbial communities associated with each <em>Armillaria</em> species may provide novel insights for managing Armillaria root disease. This study aims to identify soil microbes and their community structure around <em>A. solidipes</em>, <em>A. altimontana</em>, and western white pine (<em>Pinus monticola</em>)<em>.</em> Results of a field study revealed significant changes in microbial communities associated with two different <em>Armillaria</em> spp. Diverse and beneficial bacterial communities were highly related to the presence of <em>A. altimontana</em>, whereas trees infected with <em>A. solidipes</em> had more diverse soil fungal communities. In a greenhouse experiment, 74 western white pine seedlings were grown in five treatments: inoculated with either <em>A. solidipes</em> or <em>A. altimontana</em>, single inoculations with a delayed alternate species inoculation, simultaneous dual inoculations, and control. DNA sequences of ITS-2 and 16S rDNA were used for soil metagenomic analyses. Seedling diameter at root collar and height were recorded. Results from this study will help develop novel management approaches for suppressing Armillaria root disease by favoring beneficial microbial communities with potential biocontrol activity against <em>Armillaria </em>pathogens.</div>

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