EXACT AND NATURAL SCIENCES

Researchers prove that early Andean bean agriculture preserved the genetic diversity of the seeds

An international study revealed that the selection of desired traits and the loss of gene variation were uncoupled during the legume domestication process.


Specimens of some of the beans obtained in archaeological sites from which the ancient DNA information was extracted. Photo: courtesy researchers.

This week an international research team has published a study in Nature Plants in which they proved that bean farming carried out by the peoples who inhabited the Andes was very efficient as it achieved the selection of most of the desirable traits that are now typical of this crop, managing to preserve the genetic diversity of the seeds.

Giorgio Bertorelle, scientist at the University of Ferrara, led the study in which American, Norwegian and Argentinian researchers participated. The aim of the work was to know the genetic diversity of beans and how it varied throughout the time during the legume domestication process.

“Unlike the commonly accepted idea that the domestication of the bean was a gradual process of selection of desired traits that implied the loss of genetic diversity, we used ancient DNA to demonstrate that the selection of desirable traits and the loss of variation were uncoupled during the domestication process. The results show that early bean farming in the Andes preserved the genetic diversity of the seeds,” explains Gustavo Neme, CONICET independent researcher at the Instituto de Evolución, Ecología Histórica y Ambiente (IDEVEA, CONICET-UTN), and one of the collaborators of the study.

The scientists analyzed the genome of beans from samples obtained from archaeological sites in Mendoza (archaeological site of Gruta del Indio) and in the northeast of Argentina. A number of thirty specimens were studied. “The initial domestication of the bean took place around eight thousand years ago, both in Mesoamerica and in the central Andean area. The samples used span between two thousand five hundred and six hundred years before the present,” Adolfo Gil -CONICET principal researcher at the IDEVEA, professor of UNCuyo and collaborator of the study describes.

According to the researchers, the early agriculture of this crop was very efficient as it managed to maintain its genetic variability as a result of the use of a larger number of seeds by the first farmers as founders in each generation. The plants apparently exhibited the selected phenotypic traits, but were heterogeneous throughout the rest of the genome. The first improvement of the common bean spanned thousands of years and was assisted by crop exchanges and hybridization with wild plants. This breeding practice allowed many traits to be selected without a significant loss of genomic variation, as it happened in more recent to,es among local varieties.

“For animals and plants genetic diversity plays a key role: it is the raw material for evolution and it allows a species to solve future problems. When humans select certain traits in a particular domestic species (beans, cows, horses, corn, etc), in that process they eliminate variability to enhance some aspects. That manipulation is harmful because it loses adaptive capacity to face future possible challenges. This study proved that in Andean prehistory, during the selection process of certain traits in the bean, the species did not lose its genetic variability, which is very important for the species and the humans that manipulate it. The more genetic variability, the more possible paths open to the future in the species (in this case the bean). These results are relevant for the study of evolution and domestication of the bean, and to learn how to handle it in the future, avoiding impoverishing the genetic material of a domestic plant. Besides, this facilitates the management of the species by agronomists, ecologists and the search for variants capable of facing future environmental changes,” the researchers conclude.

References:

Trucchi, E., Benazzo, A., Lari, M. et al. Ancient genomes reveal early Andean farmers selected common beans while preserving diversity. Nat. Plants (2021). https://doi.org/10.1038/s41477-021-00848-7

About the study:

Emiliano Trucchi. Università Politecnica delle Marche, Italy.; Università degli Studi di Ferrara, Italy.

Andrea Benazzo. Università degli Studi di Ferrara, Italy

Martina Lari. Università degli Studi di Firenze, Italy.

Alice Lob. Università degli Studi di Ferrara, Italy.

Stefania Vai. Università degli Studi di Firenze, Italy.

Laura Nanni. Università Politecnica delle Marche, Italy.

Elisa Bellucci. Università Politecnica delle Marche, Italy.

Elena Bitocchi. Università Politecnica delle Marche, Italy.

Francesca Raffini. Università degli Studi di Ferrara, Italy

Chunming Xu. University of Georgia, USA.

Scott A. Jackson. University of Georgia, USA

Verónica Lema. CONICET – UNC

Pilar Babot. CONICET – UNT

Nurit Oliszewski. CONICET

Adolfo Gil. IDEVEA (CONICET – UTN) y UNCuyo

Gustavo Neme. IDEVEA (COICET – UTN). Museo de Historia Natural de San Rafael

Catalina Teresa Michieli. Universidad Nacional de San Juan

Monica De Lorenzi. Museo Arqueológico de Cachi

Lucio Calcagnile. Università degli Studi di Ferrara, Italy

David Caramelli. Università degli Studi di Ferrara, Italy.

Giorgio Bertorelle. Università degli Studi di Ferrara, Italy

By Leonardo Fernández