Award Abstract # 1601430
DISSERTATION RESEARCH: Weedy Brassica rapa in Mexico: a unique study system to investigate potential ongoing "redomestication" of a feral crop

NSF Org: DEB
Division Of Environmental Biology
Recipient: UNIVERSITY OF WISCONSIN SYSTEM
Initial Amendment Date: April 4, 2016
Latest Amendment Date: April 4, 2016
Award Number: 1601430
Award Instrument: Standard Grant
Program Manager: Samuel Scheiner
DEB
 Division Of Environmental Biology
BIO
 Directorate for Biological Sciences
Start Date: May 1, 2016
End Date: April 30, 2018 (Estimated)
Total Intended Award Amount: $19,862.00
Total Awarded Amount to Date: $19,862.00
Funds Obligated to Date: FY 2016 = $19,862.00
History of Investigator:
  • Eve Emshwiller (Principal Investigator)
    emshwiller@wisc.edu
  • Alex McAlvay (Co-Principal Investigator)
Recipient Sponsored Research Office: University of Wisconsin-Madison
21 N PARK ST STE 6301
MADISON
WI  US  53715-1218
(608)262-3822
Sponsor Congressional District: 02
Primary Place of Performance: University of Wisconsin-Madison
430 Lincoln Drive
Madison
WI  US  53706-1381
Primary Place of Performance
Congressional District:
02
Unique Entity Identifier (UEI): LCLSJAGTNZQ7
Parent UEI:
NSF Program(s): EVOLUTIONARY GENETICS
Primary Program Source: 01001617DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 9179
Program Element Code(s): 737800
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.074

ABSTRACT

This project investigates the domestication of an important food source, weedy field mustard (Brassica rapa L.). Understanding the transition from wild to domesticated plants provides both important knowledge for crop improvement and a unique opportunity to study evolutionary change because domestication often involves selection for preferred traits. Most humans rely on crops that were domesticated from wild plants thousands of years ago, which makes it a challenge to determine the dual roles of humans and environment in domestication. Examples of people domesticating plants today may provide insights into this process. The researchers will study an ongoing relationship between seven Mexican cultural groups and weedy field mustard to get at the ecological and cultural aspects of domestication. Field mustard was domesticated in Europe and Asia and selected for many diverse forms, such as turnips, bok choi, and Chinese cabbage. It is unclear which domesticated or weedy forms were introduced to Mexico and what region they were introduced from. This project integrates information from genetic data, physical measurements, chemistry, and interviews with farmers, to study an ongoing domestication process. In addition, the project will include the training of undergraduate and graduate students, and contribute to our understanding of crop domestication, food security, and control of an invasive species.

Weedy Brassica rapa provides a powerful study system to elucidate plant ferality and domestication. The availability of extensive genomic tools and the plant's short life cycle facilitate the use of inferentially powerful techniques to clarify the nature of local adaptation and artificial selection of invasive field mustard across a country-wide transect of Mexico. The research involves the novel application of RNA-sequencing, reciprocal transplant experiments, glucosinolate chemistry, and semi-structured and structure interviews, to study ongoing domestication of an important food source. Data will quantify the genetic structure and introduction history of B. rapa in Mexico, local uses and management practices of field mustard by different ethnic groups, and how different management regimes drive local population adaptation of the plant.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

             The species Brassica rapa is native to Eurasia and Africa and consists of morphologically diverse crops (e.g. turnips, napa cabbage, pak choi, oilseeds) and spontaneously occurring forms (field mustard). Despite the economic importance of B. rapa worldwide, details surrounding its wild forms, domestication, and spread as an invasive species are unclear, limiting the ability of breeders to adapt crops to new stresses and hampering control of weedy forms. Weedy field mustard in Latin America has been widely adopted by Indigenous peoples as a food and medicine and in some cases, cultures have begun to intensively collect and sow seeds in dedicated plots. This presents a study system to understand how cultures learn about newly encountered plants, which clarifies domestication as a contemporary process. We combined interviews with Mexican farmers, DNA-sequencing data, niche modeling, and a common garden experiment to investigate the following overarching questions: 1) are spontaneously occurring populations of B. rapa truly wild or feral escapes? 2) what is the domestication history of B. rapa? 3) what are the origins of invasive B. rapa? 4) how does Indigenous use, management, and preference for B. rapa vary throughout the Americas and 5) what are the evolutionary consequences of B. rapa management by Indigenous farmers in northwestern Mexico?

 

Intellectual merit:

The following summarizes the chapters of the PhD dissertation of Dr. Alex McAlvay.

 

In chapter one (published in Acta Horticulturae), we reviewed research on wild and weedy forms of B. rapa, highlighted gaps in knowledge, and suggested future courses of study. We identified the following priorities in B. rapa research: revise the taxonomy within the species, correct mislabeled germplasm in seed banks, clarify whether spontaneously occurring populations are wild or feral, and include wild forms in domestication research.

 

In chapter two, we investigated the domestication history of B. rapa crops and wild or feral nature of spontaneously occurring populations using DNA-sequencing and species distribution modeling. We analyzed the largest-to-date sampling of B. rapa crops and weedy forms. These analyses suggest that spontaneously occurring populations from the Caucasus were from truly wild populations, while those from other parts of Europe had a feral origin from European crops. Our findings also suggested an initial domestication for turnip crops near the Hindu Kush[EE1]  mountains, with subsequent spread east and west, followed by parallel selection in Europe and East Asia resulting in oilseeds and leaf crops.

 

In chapter three, we investigated the feral origins of B. rapa in Europe and reconstructed the spread of weedy B. rapa into the Americas. Our analyses of genetic structure and diversity suggested that feral B. rapa originated from European crops that hybridized with sympatric wild populations. We also found evidence that B. rapa introduced into Canada and Latin America had separate origins.  Canadian weeds were associated with northern European turnips, while Latin American weeds were associated with Mediterranean crops. We did not detect a substantial reduction in diversity from the native range to the introduced range.

 

In chapter four, we compared use, management, and preferences for B. rapa across ethnic groups in Latin America. We conducted semi-structured interviews and structured surveys with eight ethnic groups across Mexico and compared the results qualitatively and quantitatively. We found that how B. rapa is used and managed was patterned both by geographic proximity and similarity of languages. We documented several cases in which weedy B. rapa was encouraged through transplanting, sowing, and sparing from weeding. In many areas, there was evidence of declining cultivation and use of B. rapa due to changing livelihoods and availability of processed foods.

 

In chapter five, we investigated the genetic and phenotypic consequences of weedy B. rapa cultivation by Rar?muri farmers in Chihuahua, Mexico. We collected field mustard samples from 13 populations in 9 Rar?muri communities and conducted a common garden experiment and DNA-based population genetic analyses. We found significant differences in flowering time and between managed and unmanaged populations and genetic differentiation of two managed populations from unmanaged populations in the same communities.

 

Overall, our research contributes to knowledge of wild and crop genetic resources in a globally distributed multi-purpose crop species, and clarifies the domestication, feralization, invasion, recent adoption, and potential ongoing redomestication of B. rapa. These findings provide the groundwork for future studies of the genetic basis of domestication and weediness in a species with the experimental benefits of a sequenced genome, close relationship to Arabidopsis, and short life-cycle.

 

Broader impacts:

The seven undergraduates trained under this funding gained skills in species distribution modeling, genetic analysis, greenhouse experiments, and phenotypic analysis. The lead graduate student (Alex McAlvay) gained expertise in state-of-the-art bioinformatics and population genetics tools, in addition to experience with common garden experiments, phenotypic analyses, and species distribution modeling. Alex McAlvay defended and deposited his PhD dissertation in March of 2018, and is now a postdoctoral researcher at Cornell University.

 


Last Modified: 11/17/2019
Modified by: Eve Emshwiller

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