Development of an efficient genotyping-by-sequencing (GBS) library construction method for genomic analysis of grapevine

Genotyping-by-sequencing (GBS) is an outstanding technology for genotyping and single nucleotide polymorphism (SNP) discovery compared to next generation sequencing (NGS) because it can save time when analyzing large-scale samples and carries a low cost per sample. Recently, studies using GBS have been conducted on major crops and, to a greater extent, on fruit crops. However, many researchers have some problems due to low GBS efficiency resulting from low quality GBS libraries. To overcome this limitation, we developed an efficient GBS library construction method that regulates important conditions such as restriction enzymes (RE) digestion and a PCR procedure for grapevine. For RE digestion, DNA samples are digested with ApeKI (3.6U) at $75^{\circ}C$ for 5 hours and adapters are ligated to the ends of gDNA products. To produce suitable PCR fragments for sequencing, we modified the PCR amplification conditions; temperature cycling consisted of $72^{\circ}C$ (5 min), $98^{\circ}C$ (30 s), followed by 16 cycles of $98^{\circ}C$ (30 s), $65^{\circ}C$ (30 s), $72^{\circ}C$ (20 s) with a final extension step. As a result, we had obtained optimal library construct sizes (200 to 400 bp) for GBS analysis. Furthermore, it not only increased the mapping efficiency by approximately 10.17% compared to the previous method, but also produced mapped reads which were distributed equally on the19 chromosomes in the grape genome. Therefore, we suggest that this system can be used for various fruit crops and is expected to increase the efficiency of various genomic analysis performed.