Studies were conducted on inoculation of container-grown plants
with vesicular-arbuscular (VA) mycorrhizae.
Intraradical vesicles formed in colonized roots were found to
serve as propagules and significantly contribute to the infectivity
of these roots. A procedure was developed for separating
intraradical vesicles from roots; isolated intraradical vesicles were
able to colonize new host roots. Extraradical vesicles of Gigaspora
margarita were not infective propagules. Treatment of mycorrhizal
roots with sodium hypochlorite as a surface-sterilant reduced their
infectivity.
Pre-transplant inoculation of geranium with Glomus fasciculatum
resulted in spread of the endophyte within the root system and
greater and more uniform growth at flowering. Mycorrhizae were
sufficiently established on most seedlings at a minimum of 2 weeks
after emergence to persist after transplanting. Pre-transplant
inoculation increased geranium growth over that of controls transplanted into heavily inoculated soil, even when growth did not
differ at the time of transplanting.
Soilless plant growth media such as peat, bark, perlite and
vermiculite inhibited formation of VA mycorrhizae and host growth
response compared to media containing soil. Peats from different
sources varied in effects on mycorrhizal growth response of
geranium. Utilization of rock phoshate or bonemeal instead of sodium
phosphate as a fertilizer P source did not improve establishment of
mycorrhizae and host growth response in various media. Addition of
5-10% Turface, bentonite, silt loam soil or clay subsoil to peat or
vermiculite resulted in increased colonization of host roots and
significant mycorrhizal growth response, but amendment with liquid
sludge inhibited mycorrhiza formation. Differential VA mycorrhiza
formation and host growth enhancement in different growth media were
attributed to differences in equilibrium solution P concentration
after media had been saturated with fertilizer.
Growth response of geranium to inoculation with G. fasciculatum
increased with increasing pre-inoculation soil heat treatment
temperatures from 45°C to 120°C. Colonization of roots of geraniums
inoculated with G. fasciculatum was not affected by soil treatment
temperature, but treatment for 30 min at 55°C or higher eliminated
colonization by indigenous mycorrhizal fungi. The shoot P
concentration of inoculated plants relative to controls increased
with increasing temperature of soil treatment
