Spores are important propagules as well as the most reliable species-distinguishing traits of arbuscular mycorrhizal (AM) fungi. During surveys of AM fungal communities, spore enumeration and spore identification are frequently conducted, but generally little attention is given to the age and viability of the spores. In this study, AM fungal spores in the rhizosphere were characterized as live or dead by vital staining and by performing a germination assay. A considerable proportion of the spores in the rhizosphere were dead despite their intact appearance. Furthermore, morphological and molecular analyses of spores to determine species identity revealed that both viable spores and dead spores with contents were identified. The accurate identification of spores at different developmental stages on the basis of morphology requires considerable experience. Our findings suggest that surveys of AM fungal communities based on spore enumeration and morphological and molecular identification are likely to be inaccurate, primarily because of the large proportion of dead spores in the rhizosphere. A viability check is recommended prior to spore molecular identification, and the use of trap cultures would give more reliable morphological identification results. We show that the abundance and activity of AM fungi in the rhizosphere can be determined by calculating the density of viable spores and the density of spores that could germinate. The adoption of these methods should provide a more reliable basis for further AM fungal community analysis.
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This research was supported by the National Natural Science Foundation of China (31270639, 31170567), the Program for Changjiang Scholars and Innovative Research Team in University of China (IRT1035) and the Ph. D. Programs Foundation of Education Ministry of China (20110204130001).
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Spore contamination rates two weeks post inoculation. The bar chart showed the data of the proportions of contaminated spores in all germinated spores or contaminated spores in all spores that could not germinate respectively. Bars show the S.E.; n = 5 (TIFF 148 kb)
Morphological features of a crushed Funneliformis mosseae spore after staining with INT. C, spore contents; the scale bar represents 50 μm (TIFF 2834 kb)
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Sun, X., Hu, W., Tang, M. et al. Characterizing and handling different kinds of AM fungal spores in the rhizosphere. World J Microbiol Biotechnol 32, 97 (2016). https://doi.org/10.1007/s11274-016-2053-0
- Spore density
- Spore germination
- Spore identification
- Spore viability