Isolation, Culture, and Detection of Arbuscular Mycorrhizal Fungi

Abstract

This chapter summarizes methods to (i) isolate and estimate numbers of soilborne propagules of arbuscular mycorrhizal (AM) fungi, (ii) propagate AM fungi by traditional and innovative methods, and (iii) detect and assess properties of these fungi by using recent biochemical and molecular technology. Soilborne propagules of AM fungi may include chlamydospores or azygospores, colonized roots, and hyphae. Isolates of special interest should be given a unique isolate code and then classified to the species level at a later date. To observe AM structures within the root, it is necessary to clear cortical cells of cytoplasm and phenolic compounds and then to differentially stain the fungal tissue. The most commonly used methods to obtain an estimate of the total number of propagules are the most probable number (MPN) and infectivity assays. The culture of AM fungi on plants in disinfested soil, using spores, roots, or infested soil as inocula, has been the most frequently used technique for increasing propagule numbers. Conducive environmental conditions for cultures of AM fungi are a balance of high light intensity, adequate moisture, and moderate soil temperature without detrimental additions of fertilizers or pesticides. Biochemical methods have been used to improve the means of detection and quantification of AM fungi in the environment. Although current molecular methods improve our ability to detect AM fungi in the field, monitoring of the abundance and distribution of individual fungal species remains laborious and expensive.