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Colonization of Soybean by Mycorrhizal Fungi and Spore Populations in Iowa Soils
Author(s) -
Khalil S.,
Loynachan T. E.,
McNabb H.S.
Publication year - 1992
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1992.00021962008400050014x
Subject(s) - spore , colonization , rhizosphere , soil water , biology , agronomy , acaulospora , mycorrhiza , botany , arbuscular mycorrhizal , symbiosis , ecology , bacteria , genetics
Mycorrhizae, a mutualistic association between fungi of the family Endogonaceae and higher plants, have been studied extensively in the greenhouse, but much less is known about the natural ecology of these fungal‐plant associations in field soils. A better understanding of the mycorrhizae of agronomic crops is needed because of their potential involvement in systems of sustainable agriculture. This study reports on the extent of root colonization by mycorrhizal fungi, the distribution of mycorrhizal fungal spores in the rhizosphere, and the mycorrhizal fungal genera associated with soybean [ Glycine max (L.) Merr.] in 15 Iowa soils. Results indicated that soybean roots from most soils, in spite of some soils having very high soil‐test P levels, were extensively colonized (60–100%) by vesicular‐arbuscular mycorrhizal (VAM) fungi. Colonization was determined by evaluating the percentage of root segments with VAM fungi. The average colonization of plant roots from all soils was 89%, and the average Bray P1 soil‐test value was 60.3 mg kg −1 (values greater than 30.5 are considered by the Iowa State Soil Testing Laboratory to be very high). Abundant colonization was unexpected in these high‐P fertility soils because most authors report extensive colonization to occur mainly in plants growing in soils of low fertility. The VAM fungal spores were quite common in all rhizosphere soils sampled and ranged from 66 to 998 spores 100 g −1 soil. Total spore counts were significantly different among soil series ( P < 0.001) and within soil series ( P < 0.01). A negative correlation ( P < 0.05) was found between soil organic matter, P, and VAM fungal colonization. For VAM fungal genera ( Glomus , Gigaspora , Acaulospora , and Scutellospora ) were found associated with soybean rhizosphere soil. Among these, Glomus was the most abundant.