Abstract
Background : The genus Brassica mainly comprises three diploid and three recently derived allotetraploid species, most of which are highly important vegetable, oil or ornamental crops cultivated worldwide. Despite being extensively studied, the origination of the allotetraploid crops and the overall phylogeny of Brassica genus are still far from completely resolved, which has greatly hindered the development of novel Brassica crops. Here, we target and integrate the chloroplast DNA and mitochondrial DNA to investigate the genetic diversity and relationships in large plant populations centering on Brassica genus. Results : The phylogenetic analyses based on a data set including 72 de novo assembled whole chloroplast genomes, delineated a comprehensive evolutional atlas inside and around Brassica genus. The maternal origin of both B. juncea and B. carinata are monophyletic from cam-type B. rapa and B. nigra , respectively. Nonetheless, the current B. napus contains three major cytoplasmic haplotypes: the cam -type which directly inherited from B. rapa , polima -type which is close to cam -type as a sister, and the predominant nap -type. Intriguingly, nap -type seems phylogenetically integrated with certain sparse C-genome wild species, thus implying that which may have primarily contributed the cytoplasm and the corresponding C subgenome to B. napus . Human breeding creation of the B. napus cytoplasmic male sterile lines (e.g., mori and nsa ) dramatically disturbed the concurrent inheritance between mtDNA and cpDNA. Strong parallel evolution among genera Raphanus , Sinapis, Eruca , Moricandia with Brassica indicates their uncomplete divergence from each other. Conclusions : The overall variation data and elaborated phylogenetic relationships obtained herein can substantially facilitate the development of novel Brassica crops, e.g. the allotetraploid rapeseed with new cytonuclear integrations and the allohexaploid rapeseed.
Expression of nuclear and cytoplasmic genes in the progeny of a somatic hybrid between male sterile Nicotiana tabacum and N. glutinosa.