Analysis of the Structures of Mating-Type A and B Loci in Stropharia rugosoannulata Based on Genomic Data and Development of SNP Molecular Markers

Stropharia rugosoannulata is a widely cultivated edible fungus with high economic and nutritional value. It is a tetrapolar heterothallic basidiomycete. The development of single nucleotide polymorphism (SNP) markers for mating-type identification holds considerable promise for enhancing breeding efficiency. In our study, one group of test crosses and three-round mating experiments from one parental strain were conducted in order to ascertain the mating type in this species. Segregation distortion in mating types was observed after single-spore isolation, which was deviated from Mendelian inheritance. The monokaryotic strain Q25 was derived from the dikaryotic mycelium S1 of S. rugosoannulata. The genome map of strain Q25 with 48.27 Mb and 14 chromosomes was constructed using genomic, transcriptomic, and high-throughput chromosome conformation capture (Hi-C) sequencing technologies. The locations of mating-type loci were identified using genomic annotation. The mating-type A locus is located in chromosome 1, with the gene sequence of β-fg, HD2, HD1, and MIP. The mating-type B locus is located in chromosome 12. It contains five pheromone receptors and five pheromone precursor genes. Two pairs of highly specific and stable primers were designed based on SNP loci in A and B mating types. A1, A2, B1, and B2 alleles were precisely distinguished with these primers, which were subsequently applied in cultivation experiments. This study lays a foundation for the precise breeding of S. rugosoannulata.