Underground Allies: Western White Pine & Ectomycorrhizal Fungi

Underground Allies: Western White Pine & Ectomycorrhizal Fungi

Emily Martin and Lorinda Bullington
October 25th, 2019

The image above shows a western white pine root colonized by ectomycorrhizal fungi, shown at 8x magnification.

Fungi are heterotrophic organisms and are unable to produce their own food. Instead, they exude enzymes to break down organic material and absorb essential elements, like nitrogen and phosphorus, from their environment.



Ectomycorrhizal fungi (EMF) form mutualistic relationships with plant root tips (Image 1a, arrow). They grow a fungal sheath around the root, and from the sheath, hyphae extend into the soil and increase the plant’s access to water and nutrients. In exchange, the plant provides EMF with the carbohydrates they need to survive. Uncolonized root tips (Image 1b, arrow) lack a fungal sheath and the benefits that EMF provide.

EMF may also have the ability to reduce plant disease caused by insect and fungal pathogens (Bennett et al. 2017, Mateos et al. 2017). In collaboration with the Dorena Genetic Resource Center (DGRC), we hope to determine if EMF influence disease in western white pines exposed to the blister rust pathogen, Cronartium ribicola.



In September 2019, a small subset of western white pine seedlings from the DGRC experiment were harvested to evaluate the effectiveness of our EMF inoculations earlier this year (above). The seedlings were sent to Dr. Peter Kennedy’s laboratory at the University of Minnesota, where they performed the initial processing and assessment of root colonization.



After arriving at Dr. Kennedy’s laboratory, the seedlings were soaked overnight in water, removed from their containers, and evaluated for EMF colonization (Image 2, photos by Peter Kennedy).

The seedlings had a large number of roots and contained thousands of individual root tips.



White cobweb-like fuzz was observed on some seedlings. The fuzz is hyphae from inoculated ectomycorrhizal fungi that have colonized the roots (Image 3, arrows, photos by Peter Kennedy).



Each root system was cut into multiple pieces and rinsed with water to remove the soil. A portion of the roots were randomly selected for EMF quantification (Image 4, photos by Peter Kennedy). We will ‘score’ the roots by counting the number of colonized root tips. This will allow us to estimate the percent colonization of the ­­root system for each seedling. We will relate this data to disease severity next spring.



References

Bennett JA, Maherali H, Reinhart KO, Lekberg Y, Hart MM, Klironomos J. Plant-soil feedbacks and mycorrhizal type influence temperate forest population dynamics. Science. 2017 Jan 13;355(6321):181-4.

Mateos, E., Olaizola, J., Pajares, J.A., Pando, V., & Diez, J. J. (2017). Influence of Suillus luteus on Fusarium damping-off in pine seedlings. African Journal of Biotechnology, 16(6), 268-273.