– Obtaining new hybrid strains of Agaricus bisporus by crossing homokaryons from wild Mexican and commercial strains

Breeding A. bisporus is complicated due to its two pseudohomothallic and heterothallic life cycles resulting from the production of both heterokaryotic and homokaryotic basidiospores, respectively. This makes it difficult to retrieve homokaryotic offspring required for outcrossing. Mexico has a long history of using wild edible mushrooms, and mushroom cultivation, especially A. bisporus, and these practices have steadily increased in recent decades. However, the production of A. bisporus still depends on foreign cultivars. Wild collections of A. bisporus were recently reported from Mexico. This study aimed to obtain new hybrid strains of A. bisporus by crossing homokaryons from these wild strains and the homokaryon U1-7 from the commercial strain U1. Single spore isolates (SSIs) were obtained from spore prints directly from cultivated sporocarps. Putative homokaryotic SSIs were first selected based on culture morphology and confirmed using a cleaved amplified polymorphic sequence (CAPS) marker in the gene mip. Selected homokaryotic SSIs and the homokaryotic strain U1-7 were crossed. Six putative hybrid strains were obtained and tested for fruiting. Their primordia appeared after 40 to 55 days. The variability was recorded for unit weight (5.3 to 44.6 g), pileus diameter (3.3 to 8.5 cm) and pileus firmness (5.01 to 8.77 N). These are the first hybrid strains of A. bisporus obtained by crossing wild strains from Mexico.