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Bertram, Jonathan [1], Schoettle, Anna [2], Stewart, Jane [3].

The Role of Host Drought Response in White Pine Blister Rust.

Invasive fungal pathogens have the potential to thrive in ecosystems where the hosts have not coevolved resistance.  We have yet to understand how climate change and associated drought in western forests will change interactions between invasive species and their native hosts.  Cronartium ribicola, the non-native rust fungus that causes the lethal white pine blister rust (WPBR) in five-needle pines, has spread through many ecosystems in North America, aided by high fecundity and wind dispersed spores.  The life cycle of C. ribicola is complex, requiring access to two hosts and high humidity conditions.  White pine blister rust, on its alternate host, gooseberry plants (e.g., Ribes nigrum) infects leaf tissue, but is able to colonize and form cankers on branches and stems of five-needle pines (e.g., Pinus flexilis), leading to mortality.  Within the Southern Rocky Mountains, in southern Colorado, WPBR has not yet successfully established in some forest ecosystems, though it is expected to invade.  These host populations reside in harsh environments with regular, localized drought and are likely to be exposed to the effects of climate change.  Though many tree species become more vulnerable to native pathogens during water stress, and five-needle pines have mechanisms to mitigate drought effects, little is known about the interaction effects between native five-needle pines and the invasive WPBR.  As water-use changes occur, carbon storage will likely also change, affecting traits including growth, stomatal closure, and phytochemical production.   As a biotroph, WPBR depends entirely on a living host to grow, raising questions about the role of host health in infection and disease progression.  Our hypothesis is that drought stressed trees will be a reduced food source for the pathogen and will outweigh any advantages associated with reduced host defenses, leading to lower infection rates and slower overall growth WPBR within the drought stressed hosts.  This study will examine drought response and disease progression in the severely droughted, moderately droughted and well-watered P. flexilis challenged with C. ribicola.  Assessment of physiological traits of the host and quantification of fungal DNA within the host will be used to elucidate the plant-fungal interaction.  These results will provide an understanding of how host-pathogen interactions within the WPBR pathosystem may change in western forests as drought induced by climate change continue to occur.

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1 - Colorado State University, Agricultural Biology, 801 Aztec Dr Apt C, Fort Collins, CO, 80521, United States
2 - United States Forest Service
3 - Colorado State University, Agricultural Biology


Presentation Type: Oral Paper
Session: MY7, Mycology: Fungus-Plant Interactions: Arbuscular Mycorrhizae, Climate Change, and Microbiome
Location: /
Date: Friday, July 23rd, 2021
Time: 11:45 AM(EDT)
Number: MY7008
Abstract ID:831
Candidate for Awards:None

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