CLARK, RALPH. B., SHEILA K. ZETO, RICHARD. W. ZOBEL
U.S. Department of Agriculture, Agricultural Research Service, Appalachian Soil & Water Conservation Research Laboratory, PO Box 400, Beaver WV 25813-0400 USA.
Panicum virgatum was grown in pH 4 and 5 soil inoculated with eight arbuscular mycorrhizal isolates [Glomus (G.) clarum, G. diaphanum, G. etunicatum, G. intraradices, Gigaspora (Gi.) albida, Gi. margarita, Gi. rosea, and Acaulospora (A.) morrowiae] to determine effectiveness on growth and root colonization. Compared to nonmycorrhizal (nonAM) plants, mycorrhizal (AM) plants had as high as 52-fold increases in dry matter (DM) in pH 4 soil and as high as 26-fold increases in pH 5 soil; G. clarum and G. diaphanum plants had highest DM and Gi. rosea plants had lowest DM. The AM plants had higher DM when grown in pH 4 than in pH 5 soil. Root DM decreased more than shoot DM for plants grown in pH 5 compared to pH 4 soil, and shoot/root DM ratios reflected these changes. Total root length (RL) was similar for plants grown in pH 4 and 5 soil, but specific RL was higher for AM plants grown in pH 5 than in pH 4 soil. Root colonization [determined as vesicles+arbuscules inside roots (VA), hyphal infections with roots (HI), and total colonization (VA and/or HI)] varied extensively with AM isolate. Although root colonization was not related to DM, extensive DM enhancement did not occur unless total root colonization was >20%. Some AM isolates were highly effective in overcoming acidic soil constraints, and tolerance of Panicum virgatum to acidic soil may depend on root-AM symbiosis.