From genome to variety: explorations and practices of CNTC
"Owing to rapid developments in genome sequencing technologies and other omics research tools, crop improvement by whole genome analysis has become routine. However, due to the polyploidy and complexity of its genome and limited number of markers available, molecular breeding of tobacco still lags behind other crops. In this presentation, I will share our experiences on improvement of tobacco varieties conducted by the China tobacco industry. In 2010, the China National Tobacco Corp. (CNTC) initiated the “Tobacco Genome Project” with the aim to promote the green development of China’s tobacco agriculture by developing tobacco varieties with higher quality and less harmful constitutes.
In the past few years, we sequenced the genome of Nicotiana tabacum (cultivar Honghua Dajinyuan) using a strategy combing BAC-to-BAC and whole genome shotgun with around 763-fold coverage. Combining optical maps and a genetic map consisting of a set of 3,360 SNP markers, around 66% of the assembled scaffolds were anchored to pseudochromosomes. Then genomes of more than 250 tobacco varieties and landraces were resequenced and a haplotype map of genomic variations was constructed. A comprehensive tobacco gene expression atlas covering more than 100 tissues/organs under different developmental stages was presented by a custom designed gene expression array. We built a series of MS-based, multi-platform metabolomics methods, which can qualify and quantify over 500 metabolites in tobacco. A new tobacco mutant population induced by ethyl methane sulfonate mutagenesis was constructed for functional genomics applications. The genome editing system was also developed in tobacco and can be used to study gene functions on a genome scale.
The large scale genetic resources mentioned above combined with genome analyses allowed us to identify a number of genes involved in black shank and virus diseases resistance, as well as biosynthesis of flavonoid, carotenoid, precursors of NNN and phenol, etc. Understanding the functions of these genes and the performances when assembling them will be useful to conduct molecular breeding of new tobacco varieties.