“A survey of the citations suggests that authors are referring to many points we raised including the high diversity of fungi in ECM communities, dominance of some fungal types over others, and response of fungi to disturbance.”

While ectomycorrhizal (ECM) fungi and their role in plant communities have been under investigation for over 100 years, work on the below-ground aspects has been largely unfeasible. The recent progress in diagnostics using molecular tools has resulted in major advances, particularly in field-based studies. The tools were largely developed in the Bruns lab during the last 15 years or so. These tools have contributed to a renewed interest in the field with an expanding number of labs worldwide conducting research projects on ECM ecology. Within this short period of time, a number of long-standing questions about ECM fungi and their roles in plant communities have been resolved. A survey of the citations suggests that authors are referring to many points we raised including the high diversity of fungi in ECM communities, dominance of some fungal types over others, and response of fungi to disturbance. In addition, researchers cite the paper for the techniques and issues with sampling that we covered. In short, this was a timely review of a rapidly advancing field.

We reviewed the recent discoveries that resulted from the use of the molecular approaches for identifying the fungi and plants from below-ground structures. While the methods had all been published, we presented guidance and a flow chart to help researchers tailor their approaches to their questions.

During my masters research beginning in 1990, I learned that ECM fungi were influencing plant secondary succession in my system, but I could not unambiguously investigate the below-ground aspects of this interaction. At the same time, the Bruns' research group at UC Berkeley was developing molecular methods for identifying fungi from ECM root tips. It was clear to me that these tools were exactly what I needed for the next step in understanding how ECM fungi influence plant dynamics. Fortunately, the timing was perfect, as I joined the Bruns lab in 1992. In addition to the stimulating atmosphere in the lab, I found the community of researchers associated with the fields of mycology and mycorrhizal ecology extremely open, supportive, and encouraging.

ECM symbioses have been under investigation since the late 1800s, but the interaction between the fungi and the plants is cryptic, remaining largely hidden below ground in the so-called black-box. One can dig up roots and observe the presence of ECM fungi on plant roots as ectomycorrhizae, but the fungi are difficult to identify based on morphological characters. Fruit bodies of the fungi can be observed above ground, but their plant hosts are very difficult to determine. This is compounded in multi-host plant communities where the identity of a plant host may be unclear based on root morphology. Further, most of the fungal species are very difficult to maintain in culture, making field-based studies important. As a result, our understanding of the role ECM fungi play in plant dynamics remained unclear for decades. However, today we can rapidly identify the fungi using molecular techniques. As one might predict, being able to identify the organisms from root tips has led to many insights into their ecology, and there is more work to be done.