Design and testing of a plant-specific PCR primer for ecological and evolutionary studies

A polymerase chain reaction (PCR) primer, 28KJ (5-GGCGGTAAATTCCGTCC-3), was developed to specifically amplify plant DNA. This primer is located approximately 250 bases downstream of the 5′ end of the 28S ribosomal RNA gene, and it was used in combination with the universal primer 28C. The specificity of this primer combination was tested against 31 angiosperms, 9 conifers, 1 alga and 30 fungi (21 basidiomycetes and 9 ascomycetes). Both herbarium specimens and fresh samples were tested. The 28KJ/28C primer combination successfully amplified all angiosperm and conifer DNAs, but no fungal or algal DNAs. Plant DNA was amplified from plant/fungal symbioses (ectomycorrhizae of conifers and ericoid mycorrhizae of Ericaceous plants), and the plants involved in these symbioses were identified by comparing DNA sequences or restriction enzyme digest patterns of the mycorrhizal DNAs to those of known plant samples. These methods allow rapid and accurate identification of plant associates in complex plant/ fungal systems when the identity of the roots is unclear.