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Physiological response of naturally regenerated Pinus taeda L. saplings to four levels of stem inoculation with Leptographium terebrantis

John Mensah: School of Forestry and Wildlife Sciences, Auburn University

<div><em>Leptographium terebrantis</em> is an opportunistic root pathogen commonly associated with loblolly pine (<em>Pinus taeda</em> L.) stands that are undergoing a loss of vigor in the southeastern US. In order to understand the relationship between <em>L. terebrantis</em> inoculum density and host physiology, an artificial inoculation study was conducted in a five-year-old naturally regenerated loblolly pine stand over a 24 week period in a completely randomized design. We found that <em>L. terebrantis</em> caused sapwood occlusions that increased in severity as inoculum density increased. The occlusions significantly reduced water transport through the stem but did not interfere with fascicle-level stomatal conductance or induce moisture stress in the saplings. The resilience of stomatal conductance among pathogen-infested saplings is attributed to the growth and hydraulic function of new sapwood that developed after artificial inoculation. Results demonstrate that faster-growing families of loblolly pine may be capable of tolerating the vascular root disease when the formation of new sapwood is supported by sustained crown health.</div>