Construction of high-density genetic map and QTL mapping in Nicotiana tabacum backcrossing BC4F3 population using whole-genome sequencing

Backcrossing is a powerful tool for plant breeding. The improved marker-assisted backcrossing intends to transfer targeted genes or quantitative trait loci (QTLs) of interest from a donor parent into a recurrent parent. In this study, a tobacco BC4F3 population was generated using Y3 and K326 as hybrid parents and YF1-1 as F₁ parents. High-throughput sequencing data of 381 pedigree populations were used to construct high-density genetic maps containing 24 142 high-quality single nucleotide polymorphism (SNP) markers with an average genetic distance of 0.59 cM. A genome module analysis was then performed for all the offspring. A total of forty-three candidate QTLs for six agronomics traits were identified. This study provides original biomarkers for tobacco breeding and offers clues for prospective backcrossing applications in other plants.