The secondarily homothallic life cycle of the white button mushroom that results in scarcity of uninucleate basidiospores (homokaryons) in its progeny, is the most important impediment for genetic improvement of the commercial strains. Identification of homokaryons for breeding programs of Agaricus bisporus (button mushroom) is, therefore, crucial. Verifying homokaryons through fruiting trial is time consuming and unreliable. In this study, ability of RAPD markers, compared to morphological characters for identification of homokaryon isolates, was investigated. Based on morphological characters, 42 isolates were screened and exposed to RAPD markers. The results showed that RAPD markers could discriminate homokaryons from heterokaryons, based on number of bands generated. The numbers of band in homokaryons were significantly less than those of heterokaryons. Results also showed that cluster analysis, based on average of band number generated, could separate homokaryon from heterokaryon isolates. It is suggested that RAPDs could be used to identify hyomokaryons from heterokaryons for breeding program of A. bisporus.

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