Molecular analysis of arbuscular mycorrhizal community structure and spores distribution in tree-based intercropping and forest systems

Due to their potential to enhance soil biodiversity and fertility, tree-based intercropping (TBI) systems are recognized as promising agrotechnologies. However, few studies have examined the effects of TBI on the diversity of arbuscular mycorrhizal (AM) fungi. To investigate this aspect, and to compare TBI with a more typical forest plantation (FO) system, a field experiment using soybean (Glycine max (L.) Merr. cv. SO3-W4) and poplar (Populus nigra L. x A maximowiczii cv. A. Henry 'Max 5') was conducted on an arable field site in southwestern Quebec. The species of AM fungi colonizing the roots were assessed by PCR-RFLP and DNA sequence analyses of SSU rRNA genes. A total of 13 different phylotypes were identified. Phylogenetic analyses demonstrated that these belonged to the genera Glomus (11), Acaulospora (1) and Scutellospora (1). The AM fungal diversity, as expressed by the Shannon-Wiener indices, were 0.82 +/- 0.08 for the soybean and 0.70 +/- 0.11 for poplar under the TBI system. and 0.53 +/- 0.08 for poplar under the FO system. The study also investigated the distribution of AM fungal spores in the soil, and this differed in the two systems. Under the TBI system, spore abundance increased with increasing distance from the poplar trunk, while it remained relatively constant under the FO system. Our results also show that neighbouring trees and soybean plants hosted different AM fungal communities, suggesting that TBI systems may enhance AM fungal richness compared to monocultures. (C) 2008 Elsevier B.V. All rights reserved.