Genomic diversity analysis and identification of novel SSR markers in four tobacco varieties by high-throughput resequencing.

Genome resequencing was carried out on two varieties of flue-cured tobacco (LY1306 and Qinyan 96), one variety of sun-cured tobacco (Wanmao 3), and one variety of air-cured Maryland tobacco (Wufeng 1), for a comparative analysis of genomic variation across the four varieties. Single nucleotide polymorphisms (SNPs), insertions and deletions (InDels), structural variations (SVs), and copy-number variations (CNVs) were then identified in each tobacco variety. Furthermore, a functional analysis of mutated genes was carried out. Through in-depth comparative analysis of genomes of different tobacco varieties, we identified genome variations in a number of SNPs, InDels, SVs, and CNVs, respectively. Computational analysis to predict the function of mutated genes containing these differential SNPs, InDels, SVs, and CNVs showed that they were mainly involved in different functions, such as carbohydrate metabolism and secondary metabolites biosynthesis. We mainly focused on genes that were involved in the biosynthesis of secondary metabolites and nicotine metabolism. In addition, we identified five simple sequence repeat (SSR)-based markers and verified them by PCR amplification in 10 tobacco varieties. Taken together, our study increases the understanding of genetic differences between tobacco types or varieties and identifies five SSR markers to classify tobacco varieties or types.