Evaluation of the potential of trap plants to detect arbuscular mycorrhizal fungi using polymerase chain reaction-denaturing gradient gel electrophoresis analysis

Abstract

To isolate arbuscular mycorrhizal (AM) fungi from environments, the choice of appropriate trap plants is critical. The spore morphology based technique is inevitably biased because of the preference of AM fungi. In the present study, we developed a novel, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) based technique to evaluate the trapping potential of trap plants. A lateritic red soil (pH 4.5) from a citrus orchard was used for the trap culture. Clover (Trifolium repens), sorghum (Sorghum bicolor) and maize (Zea mays) were grown alone or in combination as trap plants. At harvest, AM fungal colonization, extraradical hyphal density and sporulation were measured. DNA was extracted from the roots and substrate and the 18S rDNA fragment of AM fungi was amplified, followed by DGGE analysis. Diversity and species richness were analyzed based on the DGGE profile. Sorenson’s pairwise similarity (Cs) was calculated for evaluation. Maize exhibited the lowest AM fungal colonization and extraradical hyphae density, but the highest spore number, diversity and species richness. The AM fungal diversity and species richness were higher in the substrate than in the roots. A clustering analysis based on the Cs values revealed that a combination of the three plant species detected the most AM fungi; maize was the best if grown alone. Our results suggest that this DGGE-based technique is a reliable way to select appropriate trap plants, and a combination of plant species is superior to a single species.