David Sylvia, while a researcher at the University of Florida, developed an aeroponic system for the soil-less culture of arbuscular mycorrhizal fungi and the production of sheared-root inoculum.
In the illustration below, plants are suspended in a chamber in which a mist of a
nutrient solution is generated from an atomizing disk or pressurized spray. When
all goes well, roots are amply colonized within 90 days. At harvest, roots are
removed, washed over a coarse sieve to remove and separate spores. The clean root
fragments are sheared further in a food processor. This material is collected on
a fine sieve and used as “sheared-root” inoculum.
We do not use this method, despite its obvious advantages in producing a compact clean inoculum with the potential for very high infectivity, for the following reasons:
- With over 1000 accessions, we would need a chamber for each fungus and there simply
isn’t enough space.
- So far, only a limited number of species show compatibility with this growing environment
(but also only a fraction of known culturable species have been tested in this
system). For a culture collection, any constraint on culturability of ALL germplasm
prohibits its general usage.
- Long-term storage of sheared-root inoculum is problematic, and would required much additional experimentation to work out optimum procedures. So far, the only species which has passed the rigor of all these steps is Rhizophagus intraradices, a species which also grows well in other exotic environments such as root organ culture. Any species in this genus likely is amenable to this culture method and storage since they all produce abundant spores in roots.
Sylvia, D.M. and D.H. Hubbell. 1986. Growth and sporulation of vesicular-arbuscular mycorrhizal fungi in aeroponic and membrane systems. Symbiosis 1:259-267.
Sylvia, D.M. and A.G. Jarstfer. 1992. Sheared-roots as a VA-mycorrhizal inoculum and methods for enhancing plant growth. U.S. Patent 5,096,481. Issued March 17, 1992.
Sylvia, D.M. and A.G. Jarstfer. 1992. Sheared root inoculum of vesicular arbuscular mycorrhizal fungi. Applied Environmental Microbiology 58: 229-232.
Jarstfer, A.G. and D.M. Sylvia. 1994. Aeroponic culture of VAM fungi. pp. 427-441. In: Mycorrhiza: Structure, Function, Molecular Biology, and Biotechnology. A.K. Varma and B. Hock (eds). Springer-Verlag, Berlin.