Figure 1. Frequency of Fungal
Symbiont Types in Orchid Roots

Top: Each letter represents a unique combination of fungal RFLP patterns. These patterns were produced by direct PCR amplification from orchid tissue of the fungal ITS region of the nuclear ribosomal repeat by PCR and subsequent digestion with 3 restriction enzymes (see text). The fact that there is zero overlap in fungal symbiont types in these four co-occuring orchids over the entire geographic range sampled shows that there is a high level of specificity toward particular fungi in these orchids in nature. Bottom: The lettering sequence of symbiont types is the same here. Matching symbols in the boxes indicate that these symbiont types have identical ITS RFLP paterns for that enzyme (they do not share patterns for all enzymes, or they would not be called different "types"). This figure shows that there is greater sequence similarity in various symbiont types found in the same orchid species, than between symbiont types found in different orchid species. That is, it appears that a particular orchid species "focusses" specifically on a set of related fungi in forming its mycorrhizal relations.

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