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Oyster mushrooms are grown commercially worldwide, especially in many developing countries, for their easy cultivation and high biological efficiency. Pleurotus cornucopiae is one of the main oyster mushroom species because of its gastronomic value and nutraceutical properties. Cap color is an important trait, since consumers prefer dark mushrooms, which are now represented by only a small portion of the commercial varieties. Breeding efforts are required to improve quality- related traits to satisfy various demands of consumers. Here, we present a saturated genetic linkage map of P. cornucopiae constructed by using a segregating population of 122 monokaryons and 3,449 single nucleotide polymorphism (SNP) markers generated by the 2b-RAD approach. The map contains 11 linkage groups covering 961.6 centimorgans (cM), with an average marker spacing of 0.27 cM. The genome of P. cornucopiae was de novo sequenced, resulting in 425 scaffolds (>1,000 bp) with a total genome size of 35.1 Mb. The scaffolds were assembled to the pseudochromosome level with the assistance of the genetic linkage map. A total of 97% SNP markers (3,357) were physically localized on 140 scaffolds that were assigned to 11 pseudochromosomes, with a total of 32.5 Mb, representing 92.5% of the whole genome. Six quantitative trait loci (QTL) controlling cap color of P. cornucopiae were detected, accounting for a total phenotypic variation of 65.6%, with the highest value for the QTL on pseudochromosome 5 (18%). The results of our study provide a solid base for marker-assisted breeding for agronomic traits and especially for studies on biological mechanisms controlling cap color in oyster mushrooms. IMPORTANCE Oyster mushrooms are produced and consumed all over the world. Pleurotus cornucopiae is one of the main oyster mushroom species. Dark-cap oyster mushrooms are becoming more and more popular with consumers, but dark varieties are rare on the market. Prerequisites for efficient breeding programs are the availability of high-quality whole genomes and genetic linkage maps. Genetic studies to fulfill some of these prerequisites have hardly been done for P. cornucopiae. In this study, we de novo sequenced the genome and constructed a saturated genetic linkage map for P. cornucopiae. The genetic linkage map was effectively used to assist the genome assembly and identify QTL that genetically control the trait cap color. As well, the genome characteristics of P. cornucopiae were compared to the closely related species Pleurotus ostreatus. The results provided a basis for understanding the genetic background and marker-assisted breeding of this economically important mushroom species. [ABSTRACT FROM AUTHOR]

Oyster mushrooms have a high biological efficiency and are easy to cultivate, which is why they are produced all over the world. Cap color is an important commercial trait for oyster mushrooms. Little is known about the genetic mechanism of the cap color trait in oyster mushrooms, which limits molecular breeding for the improvement of cap color-type cultivars. In this study, a 0.8-Mb major quantitative trait locus (QTL) region controlling cap color in the oyster mushroom Pleurotus cornucopiae was mapped on chromosome 7 through bulked-segregant analysis sequencing (BSA-seq) and extreme-phenotype genome-wide association studies (XP-GWAS). Candidate genes were further selected by comparative transcriptome analysis, and a tyrosinase gene (PcTYR) was identified as the highest-confidence candidate gene. Overexpression of PcTYR resulted in a significantly darker cap color, while the cap color of RNA interference (RNAi) strains for this gene was significantly lighter than that of the wild-type (WT) strains, suggesting that PcTYR plays an essential role in cap color formation. This is the first report about fine mapping and functional verification of a gene controlling cap color in oyster mushrooms. This will enhance our understanding of the genetic basis for cap color formation in oyster mushrooms and will facilitate molecular breeding for cap color. [ABSTRACT FROM AUTHOR]