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Cassava diversity

CIAT conserves the world’s largest and most diverse collection of cassava (Manihot esculenta).

To people who don’t eat cassava, or who only know it as starchy tapioca, it can come as a surprise that roughly half a billion people in Africa and Latin America and the Caribbean depend on this root crop for food, and millions of Asian farmers grow it for industrial markets.

Those who depend on cassava for food and income also depend on its diversity. Over 37% of the cassava diversity held in CIAT’s genebank originates from Colombia, with another 24% coming from Brazil, where cassava was domesticated several thousand of years ago. Other South American countries (21%), Central America and the Caribbean (7%), but also Asia (7%) are other geographic regions that have contributed to the collection. African germplasm is conserved at the IITA genebank in Nigeria.

 

Cassava can withstand harsh conditions, making it a reliable crop in difficult environments and enabling smallholder farmers to adapt to climate change. In sub-Saharan Africa, the rugged root crop will brush off expected temperature rises of up to 2 degrees Celsius by 2030 – and could be even more productive thanks to climate change. Despite being able to produce its starch-rich roots in poor soils and with little water, investment in cassava research has been dwarfed by decades of research into better-known cereal staples.

Pests and disease – cassava’s Achilles’ heel – have been the principal focus of research attempting to capture useful traits from genebank accessions, although provitaminA and dry-matter content of roots have also received considerable attention.

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Accessions

Countries of origin

M. esculent accessions

Wild-relative accessions

Cassava germplasm distributed since 1979

6,492 accessions (43,458 samples) distributed to 84 countries

All distributed materials have cleaned and checked to be free of Common Mosaic Disease, Cassava Virus X Disease, and Frog Skin Disease.

Safety backups

Cassava cannot be backed up at the Svalbard Global Seed Vault in Norway because most accessions are preserved in a “living genebank”consisting of small plantlets growing in vitroin test tubes. We thus regularly send test tubes with copies of accessions to CIP, our partner CGIAR Center in Peru. In return, CIAT’s genebank takes care of the in vitro safety duplicates of CIP’s sweet potato collection. We also keep so-called ‘bonsai’ copies of all accessions in the greenhouse, just in case.

Our impact

In 2003, CIAT and partners released a cassava variety (Nataima-31) derived from a cross between two genebank accessions and bred for whitefly resistance, high yield and good cooking qualities. It out-yields farmers’ varieties (33 t/ha) without pesticide applications and is now grown commercially in Colombia, Ecuador, and Brazil.
Estimates suggest that income generated between 1993 and 2011 by cassava growers in Thailand from the widely sown variety KU 50 totalled $1.56 billion dollars. KU 50 was developed from a cross between a CIAT genebank accession and a local Thai variety.
According to 2015 estimates, the adoption of improved cassava varieties developed by CIAT and national partners by using genebank materials has reached nearly 100% in Thailand and over 90% in Vietnam.
CIAT scientists have identified a particular form of the so-called waxy gene derived from a cassava genebank accessions. Varieties containing two copies of this gene produce a variety of starch that is inhigh demand in the food industry.

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