Course Syllabus: EFB 428/628 -- Diversity of Mycorrhizal Symbioses

Dr. Tom Horton


Lecture Monday, 10:35 - 11:30, Bray Hall rm 313

Lab Monday, 1:50 - 4:50, Illick rm 306

Paper discussion Wednesday, 10:35 - 11:30, Bray Hall rm 313


Required books (I have reserve copies that you can use in class):

Smith and Read (2009) Mycorrhizal Symbioses 3rd edition.

This is THE authority on mycorrhizal associations. It covers everything. The literature list at the back is as complete as you will find.

Peterson, Massicotte and Melville (2004) Mycorrhizas: Anatomy and Cell Biology.

I believe you will find this book very helpful in the first part of the course as we survey mycorrhizal diversity. It is organized by mycorrhizal type, just like the lecture topics.




EFB 428

Midterm exam = 100 pts

Lab notebook (20pts on anatomy, 20pts on DNA, 10pts on clarity & thoroughness) = 50 pts

Lab practical (anatomy and technique) = 50 pts

Paper questions, 10 papers w/5 questions each = 50 pts

Term paper (5 – 10 pages) = 100 pts

Final Exam = 100 pts

Total = 450 points

  Extra credit: Up to 20 pts for a serious effort at the Mushroom fair at Beaver Lake, Sunday September 29


EFB 628

Midterm exam = 100 pts

Paper presentations (lead 2 at 15pts each, overall contributions at 20pts) = 50 pts

Lab practical (anatomy and technique) = 50 pts

Manuscript (Bioassay II experiment) = 150 pts

Final Exam (Oral format) = 100 pts

Total = 450 pts

  Extra credit: Up to 20 pts for a serious effort at the Mushroom fair at Beaver Lake, Sunday September 29




Monday Date shown


Mon, 10:35-11:30


Wed, 10:35-11:30


Mon, 1:50 – 4:50

Aug 27

General Overview, Mycology and root anatomy




(It’s about fish, but the message applies here as well)


Bioassay I - Pine inoculated with soil from Rome Sand Plains. We will identify unknown fungi from these roots (see Labs from Oct. 29 on).

Bioassay II - Pine inoculated with soil from Rome Sand Plains. Grow under varying fertilizer levels. Response variable = % colonization. Use these data for final paper.

Sept 3

No Class – Labor Day

No Lab - Labor Day

Sept 10

Ectomycorrhizae (EM)


The long and short of EMF spore dispersal

Field trip to Rome Sand Plains to collect EM root tips and sporocarps

Sept 17

Ericoid,Arbutoid and Monotropoid mycorrhizae



  1. Identify genus (species) of sporocarps from Rome Sand Plains, preserve specimens
  2. Mycorrhizal root anatomy: Sectioning EM and orchid mycorrhizae




Sept 24

Ericoid,Arbutoid and Monotropoid mycorrhizae (continued)


Mycorrhizal anatomy survey: ectomycorrhizae, monotropoid, arbutoid, ericiod,



BEAVER LAKE 9/30 Collect fungi on Saturday, bring them in and help set up on Sunday. I'll be at Beaver Lake on Sunday starting at about 10am, show runs 1-4pm.

Oct 1

Ericoid,Arbutoid and Monotropoid mycorrhizae (continued - again!)

Transfer of carbon from willow and birch to an achlorophyllous orchid

Bring in a plant and we will clear and stain the roots for AMF


Look at Orchid Roots


Generally prepare for Lab Practical on Ocr. 22. Bring in roots and look for all the structures, types, etc.


Oct 8


Sarcodes - Mutualist or parasite?

View AMF from last week

Look at Orchid Roots


Generally prepare for Lab Practical on Oct. 22. Bring in roots and look for all the structures, types, etc.


Oct 15


Dan Clune (Material from this lecture will not be included in Exam I)


Oct 22

Exam I: Mycorrhizal types


  • Lab Practical: Mycorrhizal root anatomy

(Open Notebook)

  • Undergrads -- Turn in Notebook for Anatomy grade after Practical


Oct 29


Molecular techniques revolution

  • Cancelled

Nov 5

Molecular techniques cont.



DNA Lab I - DNA Extraction & PCR

Nov 12

Molecular techniques cont.

Maria Harrison guest lecture



  1. DNA Lab II - Run gels to check for PCR products & Set up restriction digests (RFLP)
  2. Harvest fertilizer experiment; quantify mycorrhizal colonization



Nov 19

No Class - Thanksgiving


Nov 26


Commercial inoculum

Review of PCR - based methods



Dec 3

Mon 12/3 General Review


No class on Wed 12/5

Monday 12/3 in Lab:

1. Lab Practical...part II, worth 20 points and focused on AMF and PCR-based methods

2. Graduate team report to class on the Bioassay experiment

Final Exam : Thursday, 12/13 12:45-2:45, Bray Hall room 313



































































Welcome to Mycorrhizal Ecology! It is amazing to me that most textbooks on Plant Physiology, Botany and Ecology barely mention mycorrhizal symbioses. Indeed, many ecologists still consider mutualisms as special cases (acacia ants, orchid moths). Part of this bias comes from the fact that models of mutualisms predict they are ecologically and evolutionarily unstable and therefore should not be common (there are probably some socio-political issues here as well!!). But four examples of very stable mutualisms should put that misunderstanding to rest: mitochondria, chloroplasts, N-fixing bacteria in plant roots, and lichens. N-fixation nodules and lichen mutualisms each evolved independently several times. Further, around 80% of the world’s plant species associate with mycorrhizal fungi that are typically mutualistic, also evolving multiple times, and a fifth case demonstrating the ubiquity of mutualisms in nature.

Q: Are mycorrhizal symbioses evolutionarily stable? 


Course Details

There will be a lecture and lab each Monday, and a paper discussion each Wednesday. The topics covered in the lecture, paper discussions and labs will be linked as much as possible. The first half of the semester will be an overview of mycorrhizal diversity. There are 7 main mycorrhizal types, defined/grouped based on their root anatomy and the species of fungi and plants involved: arbuscular mycorrhizae, ectomycorrhizae, ericoid mycorrhizae, orchid mycorrhizae, arbutoid mycorrhizae, monotropoid mycorrhizae. We will cover one of these types each week (see schedule), giving you a firm foundation of these root symbioses. We will then use this foundation in the second half of the semester to investigate the roll of mycorrhizal fungi on ecosystem functions, seedling establishment, plant invasions, edible fungi, etc. I am open to suggestions, so send me your ideas.


Q: Some use mycorrhizae for the plural form of mycorrhiza while others use mycorrhizas. Who is correct and why?


We are lucky enough to have this course as a regular offering here at ESF. It is probably the ONLY course dedicated to mycorrhizal symbioses taught regularly in the country. I hope the topic grabs your attention as much as it did mine back in 1990 (!!) when I started my masters degree.