Abstract:
A study was conducted to characterize the vesicular-arbuscular
(VA) fungi of apples grown in Oregon. Using roots and soil from
apple orchards as inoculae, six different fungal species were found
in pot cultures: Gigaspora margarita Becker and Hall, Glomus fasciculatum
(Thaxter sensu Gerdemann) Gerd. and Trappe, Glomus mosseae
(Nicol. and Gerd.) Gerd. and Trappe, Gigaspora calospora (Nicol. and
Gerd.) Gerd. and Trappe, Glomus monosporum Gerd. and Trappe and
Sclerocystis rubiformis Gerd. and Trappe. The first three species
grew out of apple root inoculum, suggesting that they are strong
competitors in colonizing apple roots in the field. Gigaspora margarita
has not heretofore been reported in Oregon.
The effectiveness of Gigaspora margarita, Glomus fasciculatum
and Glomus mosseae and applied P in promoting growth of apple seedlings
grown in two soils which differ in their available P content
was studied in a greenhouse experiment. Mycorrhizal inoculation
could substitute for P application in low P soil with G. fasciculatum
being the most effective in promoting growth and P uptake, G.
margarita being the least effective, and G. mosseae intermediate.
Also studied were the effects of soil-applied P and VA mycorrhizae
on nutrient uptake and growth of maize grown in Willamette soil.
Both treatments enhanced plant growth and P uptake. VA mycorrhizal
inoculation significantly increased percent leaf Mg and Mn over the
controls. Application of P to one-half of the root system did not
reduce percent root colonization by VA mycorrhizae in the other
half, while combining both treatments reduced percent root colonization.
