RAPD discrimination of Agaricus bisporus mushroom cultivars

Cultivars of the white button mushroom Agaricus bisporus are difficult to d ifferentiate, which has made strain protection problematic for this crop sp ecies. We have used RAPDs to discriminate between 26 strains of A. bisporus . 24 of which were commercial cultivars, and to characterise the genetic re latedness of these strains. Using 20 primers, 211 RAPD markers were identif ied and used in hierarchical cluster, patristic distance and parsimony anal yses. All strains could be differentiated using the aggregated primer data. Although no one primer could differentiate all 26 strains, several individ ual primers yielded unique fingerprints for a variety of strains. The great est differences (up to 28% variation) were observed in comparisons with or between two wild collections of A. bisporus. Quondam cultivars, commercial brown and off-white varieties proved more variable than the widely grown 'h ybrid' types. Of the 15 hybrid varieties analysed, only one differed substa ntially (20% or more variable). The patristic and parsimony analyses both d emonstrated the gross similarity of the hybrids, many of which appear to be essentially derived varieties from two original hybrid cultivars. RAPD ana lyses can assist mushroom strain identification and could play a role in th e protection of novel cultivars.