True morels (Morchella spp.) are a group of edible fungi that are in high demand worldwide. However, this group of fungi remains poorly understood in terms of its genetic structure, life cycle, and mating system. In the present study, we cloned the MAT locus in Morchella sp. Mes-20 using long-range polymerase chain reaction (PCR) amplification. Our results showed that the MAT1-2 idiomorph in the single-ascospore isolate YAASMCB-3 was 7.5 kb in length, harboring a single MAT1-2-1 gene, whereas the MAT1-1 idiomorph in the isolate YAASMCB-15 was 7.8 kb, carrying both MAT1-1-1 and MAT1-1-10 genes. Mating-type diagnostic assays of single-ascospore populations confirmed that Mes-20 is heterothallic. In addition, 42 collections belonging to 17 morel species (7 black morel species [Elata clade], 9 yellow morel species [Esculenta clade], and 1 species from the Rufobrunnea clade) were used to clone and characterize the MAT1-1-1 and MAT1-2-1 genes for development of the mating gene genealogies. In concordance with the multilocus phylogenetic trees, collections for the respective species were readily distinguished by well-supported lineages in mating gene genealogies. The topologies were consistent within the Elata clade, whereas the branching order and sister-group relationships slightly varied within the Esculenta clade. Our results show that species in the genus Morchella could be delimited by mating gene genealogies.
Keywords: Ascomycota; heterothallism; idiomorph; mating gene genealogies; true morels.