Randomly amplified polymorphic DNA using the M13 core sequence of the vesicular–arbuscular mycorrhizal fungi Gigaspora margarita and Gigaspora gigantea

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Abstract
Vesicular–arbuscular mycorrhizal (VAM) fungi are obligate symbionts, and a primary benefit provided to the host is the alleviation of stress. The recalcitrance of these fungi to grow in pure culture has spurred researchers to develop an alternative form of cultivation, namely the root organ culture (ROC). This synthetic form of production is new and efforts were made to use randomly amplified polymorphic DNA with the M13 minisatellite sequence as the polymerase chain reaction primer to look into polymorphism, if any, in the spores of Gigaspora margarita produced both in vitro and in situ (soil). The fingerprint patterns obtained from in vitro and in situ spores were similar. Extramatrical structures, such as auxiliary cells, were also examined by DNA fingerprinting. Their amplification pattern did not vary from the mother or daughter spores. A few interesting observations were made. For instance, the mother spore, which seemed hollow and inactive after germination, nevertheless contained nuclei after 4 months under in vitro conditions and generated a fingerprint pattern. The fingerprint pattern for Gigaspora margarita was different from that of Gigaspora gigantea, indicating that the minisatellite sequence could be exploited for identifying VAM fungi. ROC appears to be a truly representative system, in the sense that it mimics the essential features of the complex rhizosphere, allowing the fungi to complete their life cycle without any induced genetic changes per se. Key words : root organ culture, arbuscular mycorrhiza, M13 minisatellite sequence, randomly amplified polymorphic DNA.