PPDL Picture of the Week for

March 2, 2015


Dan Egel, Vegetable Pathologist, SWPAC, Botany & Plant Pathology, Purdue University

The photograph above is of fungal spores that form a beneficial association with roots of plants.  The name of this association is known as mycorrhiza (mycorrhizae, plural).  The fungus helps the plant take up nutrients, particularly phosphorus, and the fungus gets carbohydrates (sugars) from the plant.  Mycorrhizae are particularly helpful in barren soils such as one might encounter in mining waste.  There is some evidence that these fungi may help in disease and drought resistance as well. 

In general, there are two types of mycorrhizal associations.  The spores of the fungi shown here enter into the roots of the plants and grow between cells.  This type of association is known as endo-mycorrhizae.  These fungi specialize in associations with plants such as oak and beach trees as well as with some herbaceous plants.  Other fungi specialize with trees such as pines and grow on the outside of the root like a sheath.  In some cases, it is possible to see the mushrooms of mycorrhizal fungi surrounding the host tree. 

Gardeners may be wondering how to get mycorrhizae into their gardens.  A quick search of the Internet shows that there are many products that are mycorrhizal inoculants (if you purchase a product, follow the directions carefully).  However, mycorrhizal fungi are common in most soils and will form an association with plants if given a chance.  To encourage mycorrhizal associations in your garden, take good care of your soil.  Add organic matter, for example, by using cover crops.  Avoid over fertilization.  Use a good rotation in vegetable gardens.  

The next time you see mushrooms of the same type popping up around a tree, remember that the mushrooms may be forming mycorrhizae with the roots under the soil. 

​Click image to enlarge

1 tn 
A. Glomus fasciculatus; Magnified 440X
B. Glomus etunicatus; Magnified 315X
C. Glomus mossae; Magnified 160X
D. Gigaspora rosae; Magnified 160X
Photo credit: Denise Fardelmman Egel​