| Summary: | Sugi (<i>Cryptomeria japonica</i> D. Don) is an important forestry species in Japan. <i>C. japonica</i> ‘Spiralis’ is a mutant with twisted needles. The mutant is called Yore-sugi in Japan and is known as ‘Rasen’ in other countries. The twisted trait is regulated by a dominant gene called <i>TWISTED NEEDLES</i>, and it can be identified by observing the needles within 1 to 2 months after germination. The <i>TWISTED NEEDLES</i> gene may be useful for improving the efficiency of genome editing technology in <i>C. japonica</i>. In this study, we attempted to identify the linkage group of the <i>TWISTED NEEDLES</i> locus and investigate markers that sandwich this locus using the mapping family. First, we identified the linkage group containing the <i>TWISTED NEEDLES</i> locus based on the distortion from the expected segregation ratio using 32 mutant individuals of the mapping family. The segregation distortion showed that the <i>TWISTED NEEDLES</i> locus was located on the 11th linkage group (LG11). Next, a linkage map of LG11 was constructed based on genotype data from the single-nucleotide polymorphism (SNP) markers and double digested restriction site-associated DNA sequencing (ddRAD-seq) using 123 individuals of the MMY-1 family. On this map, six markers were located at the same position as the <i>TWISTED NEEDLES</i> locus. To investigate markers sandwiching the <i>TWISTED NEEDLES</i> locus, a partial linkage map around the <i>TWISTED NEEDLES</i> locus was constructed using 643 individuals of the MMY-1 family. The <i>TWISTED NEEDLES</i> locus was located in the 0.6 cM region between gSNP01822 and the other five markers (Contig_4705-179, Contig_4518-93, Contig_4398-118, gSNP04056, and Contig_4970-113).
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