Localization of TWISTED NEEDLES Locus on Linkage Map of Japanese Cedar (Cryptomeria japonica D. Don)

Abstract

Sugi (Cryptomeria japonica D. Don) is an important forestry species in Japan. C. japonica ‘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 TWISTED NEEDLES, and it can be identified by observing the needles within 1 to 2 months after germination. The TWISTED NEEDLES gene may be useful for improving the efficiency of genome editing technology in C. japonica. In this study, we attempted to identify the linkage group of the TWISTED NEEDLES locus and investigate markers that sandwich this locus using the mapping family. First, we identified the linkage group containing the TWISTED NEEDLES locus based on the distortion from the expected segregation ratio using 32 mutant individuals of the mapping family. The segregation distortion showed that the TWISTED NEEDLES 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 TWISTED NEEDLES locus. To investigate markers sandwiching the TWISTED NEEDLES locus, a partial linkage map around the TWISTED NEEDLES locus was constructed using 643 individuals of the MMY-1 family. The TWISTED NEEDLES 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).