O.A. MEDINA¹, A.E. KRETSCHMER, Jr² and D.M. SYLVIA¹

¹Dept. of Soil Science, University of Florida, Gainewille, FL 32611
²University of Florida, Agricultural Research and Education Center, P.O. Box 248, Ft. Pierce, FL 33454.

Abstract

A survey was conducted to quantify percentage root colonisation, spore density, and the species distribution of vesicular-arbuscular mycorrhizal (VAM) fungi associated with cultivated tropical forage legumes in south Florida. Root and rhizosphere soil samples of 4 tropical forage legumes were collected from October 11 to 17, 1984, at 4 locations. Total spore density ranged from 5 to 679 per 100 g of air-dried soil, and the percentage root colonisation varied from 3 to 41%. Legume species differed in percentage root colonisation and total spore density among locations except for Desmodium heterocarpon DC. cv. Florida (carpon desmodium), which showed little difference among locations in percentage root colonisation. Fort Pierce had the highest total spore density for all legume species except Macroptilium atropurpureum Urb. cv. Siratro.. Six species of VAM fungi were collected in this survey: Gigaspora heterogama Gerdemann & Trappe, Gigaspora margarita Becker & Hall, Glomus etunicatum, Becker & Gerdemann, Glomus intraradices Schenck & Smith, Glomus sp. and Acaulospora spinosa Walker & Trappe. The occurrence of VAM fungal species, as determined by spore numbers, was affected by the legume host and location.