Brassica rapadomestication: untangling wild and feral forms and convergence of crop morphotypes

Abstract

The study of domestication contributes to our knowledge of evolution and crop genetic resources. Human selection has shaped wild Brassica rapa into diverse turnip, leafy, and oilseed crops. Despite its worldwide economic importance and potential as a model for understanding diversification under domestication, insights into the number of domestication events and initial crop(s) domesticated in B. rapa have been limited due to a lack of clarity about the wild or feral status of conspecific non-crop relatives. To address this gap and reconstruct the domestication history of B. rapa, we analyzed 68,468 genotyping-by-sequencing-derived SNPs for 416 samples in the largest diversity panel of domesticated and weedy B. rapa to date. To further understand the center of origin, we modeled the potential range of wild B. rapa during the mid-Holocene. Our analyses of genetic diversity across B. rapa morphotypes suggest that non-crop samples from the Caucasus, Siberia, and Italy may be truly wild, while those occurring in the Americas and much of Europe are feral. Clustering, tree-based analyses, and parameterized demographic inference further indicate that turnips were likely the first crop type domesticated, from which leafy types in East Asia and Europe were selected from distinct lineages. These findings clarify the domestication history and nature of wild crop genetic resources for B. rapa, which provides the first step toward investigating cases of possible parallel selection, the domestication and feralization syndrome, and novel germplasm for Brassica crop improvement.

Agricultural weeds: the contribution of domesticated species to the origin and evolution of feral weeds

“…Recently, many wild populations from America, Europa, and Asia have been shown to be true endo-and exoferal populations. 141 This species is cited as a weed in more than 20 crops in over 50 countries in the northern hemisphere, several Asian countries, South America, and in Australia and New Zealand. 141,142 Herbicide resistance was first detected in Canada in 1977, in a B. rapa biotype resistant to atrazine.…”

“…141 This species is cited as a weed in more than 20 crops in over 50 countries in the northern hemisphere, several Asian countries, South America, and in Australia and New Zealand. 141,142 Herbicide resistance was first detected in Canada in 1977, in a B. rapa biotype resistant to atrazine. Later, in 2012 the first glyphosate resistance was reported for this species, in Argentina, but the origin of this resistance was confirmed to be transgenic.…”

Transposable element insertion: a hidden major source of domesticated phenotypic variation in Brassica rapa

“…During domestication over a long period in Europe as well as in Asia, the species has provided a rich source of phenotypic variants responding to various climatic conditions (Warwick, 2011). For example, turnips that form enlarged roots are biennial and require vernalization to flower (Zhang et al ., 2014); the B. rapa oilseed crops that are used for oil extraction establishes annual spring and biennial winter types (McAlvay et al ., 2021); Chinese cabbages that form leafy heads vary in annual/biennial habit, presenting spring, summer, and autumn ecotypes (Su et al ., 2018); and one East Asian vegetable crop caixin that is selected from pak choi (Cheng et al ., 2016) bolts rapidly to form long and tender floral stems (Cheng et al ., 2014; Zhao et al ., 2005). These diverse morphological configurations represent important agronomic traits in B. rapa .…”

Genetic Analysis Reveals Three Novel QTLs Underpinning a Butterfly Egg-Induced Hypersensitive Response-Like Cell Death in Brassica Rapa

“…Brassica nigra, and other Brassica crops raise questions on the role of crop domestication on this defence trait. Brassica crops are characterized by an extraordinary intraspeci c diversity in morphotypes which differ signi cantly from the progenitor wild relatives as result of domestication [92][93][94]. The selection for speci c crop morphotypes has often targeted leaf morphological and/or biochemical traits which often show trade-offs with overall plant defense traits [95,96].…”