Genomics of Domestication of Brassica rapa

Genomics of domestication of Brassica rapa

Xinshuai Qi¹, Hong An², J. Chris Pires², Michael S. Barker¹

1 Dept. of Ecology & Evolutionary Biology, University of Arizona, Tucson, AZ, USA.

2 Division of Biological Sciences, University of Missouri, Columbia, MO, USA.

Understanding the genetic changes associated with domestication is of importance both theoritically and practicially. Genus Brassica includes many important crops, like pak choi, Chinese cabbage, turnip, oilseed, broccoli, cauiflower and so on. The vast morphological variations and multiple round whole genome duplications within the genus make Brassica crops a good model to study domestication. Pak choi (B. rapa var. chinensis) and Chinese cabbage (B. rapa var. pekinensis) are two most important cultivars within Brassica rapa (2n = 20), however, their domestication and introduction history are still controversial, and the genetic changes and artificial selection associated with their domestication are still unclear. We sequenced transcriptomes of 162 Brassica rapa accessions around the world, with a focus on pak choi and Chinese cabbage in East Asia. Our population genomic analyses and gene differential expression data indicate a single origin of pak choi and Chinese cabbage from China followed with multiple rounds of recent introduction and hybridization events. Gene differential expression patterns in the early developmental stage are consistent with the domestication history and leaf morphological variations. We also identified genes potentially under selective sweep during domestication, which are of importance for breeding and improvement. Further studies will focus on the eastward introduction of Brassica rapafrom Mediterran, and the influence of hexaploidization on Brassica diversification.