BAKARR, MOHAMED I & DAVID P. JANOS.
Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, FL 33124, USA.
We examined effects of manipulation of arbuscular mycorrhiza
(AM) colonized root fragments (mycorrhizal fragments) on their efficacy as inoculum.
We used field collected roots and performed two separate experiments to determine
whether a) fragment size and b) age of inoculum influenced mycorrhiza formation
by suitable AM host plants.
In the first experiment, we inoculated Psidium guajava L. seedlings with
mycorrhizal fragments of 100 cm total length cut into 0.5 cm, 1.0 cm, 2.0 cm
and 4.0 cm lengths (4 treatments x 14 replicates). For each treatment, we harvested
pairs of seedlings at two-week intervals over a 14 week period, and quantified
mycorrhiza colonization in entire root systems. In the second experiment, we
added 5 g of freshly collected and chopped (1-2 cm) root inoculum to pots containing
sterile soil, and transplanted six-day old Abutilon theophrasti (Medic.)
seedlings at 0, 3, 6, 9, and 18 days after inoculation (5 treatments x 10 replicates).
We harvested each treatment 70 days after its seedlings had been transplanted.
Mycorrhizal fragments of 100 cm total length cut into four different lengths
produced different amounts of initial colonization in P. guajava L. seedling
roots. Colonization was maximized by the 1.0 cm and 2.0 cm fragments. Freshly
collected and chopped field root inoculum added to pots containing sterile soil
and planted with A. theophrasti Medic. seedlings showed a decline in
infectivity after 6 days. These results suggest that manipulation of root fragments
may affect their contribution to mycorrhiza inoculum potential (MIP) as assessed
by extractive bioassays.