Resequencing in Brassica juncea for Elucidation of Origin and Diversity

Abstract

AbstractBrassica juncea (L.) Czern. et Coss. was formed 8000–14,000 years ago by hybridization between B. rapa and B. nigra. Domestication and improvement of this species have resulted in diverse morphotypes, which produce seed oil, condiment, swollen root and stem vegetables and leafy vegetables. Various studies had been done in the past to investigate the genetic diversity and origin of B. juncea germplasm and varieties using morphological traits and biochemical markers. However, the origin and domestication of the ancient allotetraploid species B. juncea remain uncertain. The genome sequence of three types B. juncea has been reported, which provides an opportunity to resolve the origin, domestication and diversification of B. juncea. Genetic variation in mustard was identified by resequencing of 480 global accessions. Population genetic and phylogenetic analyses revealed evidence for three clade and six distinct genetic groups. Nuclear and organelle genomic analyses supported a monophyletic origin of B. juncea in West Asia. During mustard eastward spread following three independent migrations, new forms were evolved by gene mutations and introgressions. Sweep scan, genome-wide association study and RNA seq identified causal variants and genes for flowering time and morphological variations associated with domestication and diversification of the versatile mustard. In this chapter, we provide comprehensive insight into the diversity, origin and domestication of B. juncea.Keywords Brassica juncea Genome resequencingOrigin centerGenetic diversityGWASSelective sweep