A research collaboration between The University of Warwick, the Smithsonian Institution and Embrapa (Brazilian agricultural research), has shown that thousands of years of farming myths and cultural traditions have been key to the survival of the cassava crop (the source of tapioca).

Cassava (also called Yuca or Manioc) is a root vegetable that feeds around a billion people worldwide. It thrives in poor soil, drought conditions and pest-prone environments, making it an essential crop in difficult climates. It is grown worldwide via stem cuttings, a method that produces new cassava plants that are genetic clones of the original. Clonal planting is expected to result in low genetic diversity, which leads to plants becoming vulnerable to diseases.  

In this article published in ScienceLink opens in a new window, analysis of the genomes of more than 500 modern, herbarium and archaeological cassava plants found the cassava genome to be extraordinarily diverse for a clonal crop. 

To understand how this genetic diversity arose, researchers looked to indigenous Brazilian farmers for answers. Through interviews, they found that local cultural practices and traditions have been responsible for creating and maintaining the varied cassava gene pool.  

Senior author of this paper, Professor Robin AllabyLink opens in a new window of The University of Warwick, said: “This study really shows the importance of small-scale indigenous farming to our global food security.” 

For example, indigenous farmers discussed their belief in Kukurro, the caterpillar god with whom they decorate their farming implements. In Kukurro’s honour, farmers occasionally plant stems of high-yielding and resilient cassava plants in close proximity in special ‘Kukurro houses’. This enables seed-based sexual reproduction, resulting in ‘cassava from the sky’, rescuing genetic diversity to the system.

Dr Logan Kistler from the Smithsonian Institution and first author, said: “We wondered if this practice of cloning stem cuttings would keep diversity low, since reproducing by seed is a way of reshuffling the genetic deck and folding in new variation. We saw the total opposite: cassava has even more diversity than its wild relatives because of how people have prioritised and maintained diverse varieties.” 

Similar patterns of cassava diversity were found across the different areas of the Amazon region and Caribbean; this is unusual as regional genetic variation is common in widespread crops. This was explained by the farmers’ reports of exchanging and trading cuttings of different cassava varieties, resulting in regional distribution of resilient and diverse crops. This cultural practice is so engrained that, as part of the marriage custom for the Brazilian Waurá people, new brides bring Cassava cuttings to their husband’s village. 

Dr Fábio de Oliveira Freitas, EMBRAPA researcher, said: “Stories and myths linked with crops are a strong part of indigenous cultures. This kind of work shows how some myths can impact crop evolution, why it is so important to support those people and how much we still have to learn.” 

Developing our understanding of these indigenous biodiversity practices could inform future breeding strategies, and bolster efforts in crop conservation and food security in difficult environments.  

The full Science article can be read here: https://www.science.org/doi/10.1126/science.adq0018 

ENDS 

Notes to Editors 

Images were provided by Fábio de Oliveira Freitas

Research & Funding 

This study was done with the Waurá community in Xingu, who welcomed the researchers into their sovereign homeland and shared their knowledge and traditions.  

Computations performed for this paper were conducted on the Smithsonian Institution High Performance Cluster (https://researchcomputing.si.edu/high-performancecomputing-clusterLink opens in a new window).  

Portions of the laboratory work were conducted in, and with the support of, the Laboratories for Analytical Biology (LAB) facilities of the Smithsonian’s National Museum of Natural History. Authorization for sequencing Brazilian species was provided by SISGEN no. A725DDC. 

Funding: Funding for the research was provided by a Smithsonian Institution grant and fieldwork was funded by the National Geographic Society (NGS-61704R-19) 

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