Cassava is vital to the food security of millions of Africans who eat some form of the root crop daily. Although cassava breeders are making progress, they still face significant challenges in developing disease-resistant varieties that also increase overall yield and respond to the needs of smallholder farmers and processors. Cornell University will expand international efforts to deliver improved varieties of cassava to smallholder farmers in sub-Saharan Africa with $35 million in new funding from the Bill & Melinda Gates Foundation and UK aid from the United Kingdom.
“This grant funds a second five-year phase that will allow us to build on previous work and focus on getting improved varieties into farmers’ fields,” said Ronnie Coffman, international plant breeder and director of Cornell’s International Programs in the College of Agriculture and Life Sciences, who leads the project.
During Phase 1 of the Next Generation Cassava Breeding project — also funded by the Gates Foundation and UK aid from 2012 to 2017 — researchers shortened the breeding cycle for new cassava varieties by improving flowering and using genomic selection. Through analyzing plant genotypes and identifying cassava lines with desirable traits, such as resistance to cassava brown streak disease or high dry matter content, breeders also improved their ability to make selections based on genetics and probability without having to wait for seedlings to reach adulthood. These methods save breeding time for a crop where flowering and sexual propagation are issues.
Another goal of Phase 1 was to make cassava genomic information publicly accessible on an open database. Cassava researchers all over the world are now comparing results and improving breeding programs without duplicating efforts by using Cassavabase. To reduce cost per progeny and improve the quality of data uploaded to Cassavabase in Phase 2, NextGen researchers will use additional methods of whole genome sequencing.
“Our focus for the next five years will be to translate this research into breeding practices to increase impact,” said Chiedozie Egesi, NextGen project director and adjunct professor of plant breeding and genetics at Cornell, who is based at the International Institute of Tropical Agriculture (IITA) in Nigeria. “We have a strong gender component to Phase 2. A key goal will be to identify traits preferred by women farmers and end-users and incorporate them into new cassava lines.”
Egesi said, “We believe we will accelerate genetic gain as well as adopted genetic gain, increase the yields and resilience of cassava production by smallholder farmers, and move African cassava breeding toward greater capacity.”
“Among the 30 new clones developed at IITA using our methods, 10 had higher dry matter yield than any clone currently available for smallholder farmers in Nigeria,” said Jean-Luc Jannink, a research plant geneticist with the United States Department of Agriculture, Agricultural Research Service (USDA-ARS) and Cornell adjunct associate professor in the Department of Plant Breeding and Genetics at Cornell. “Dry matter yield is a close proxy to food yield. Conservatively, we believe that we will increase the rate of genetic gain in cassava by 30 to 50 percent.”
Said Peter Kulakow, IITA cassava breeder and geneticist: “Genetic gain is a measure of the improvement of plant performance between generations and a goal of most modern breeding programs. Swifter improvements mean more new varieties can be tested and released.”
At the sixth annual Next Gen Cassava meeting, Feb. 19-24 in Dar es Salaam, Tanzania, teams of NextGen breeders, geneticists, data analysts, computer programmers, food technologists, social scientists and crop protectionists will be focusing on goals for Phase 2 and discussing how to better coordinate and leverage the exchange of germplasm and genotypic and phenotypic data from each other.
Developing capacity for sustainable breeding programs
Compared with other major staples like maize, rice and wheat, cassava has undergone few advances in productivity and yield over the last 50 years, making it an ideal candidate for breeding improvement. Because cassava is clonally propagated and has a low multiplication rate, it can take almost six to eight years before a new cassava variety makes it from breeders’ nurseries through field trials to farmers’ fields. Most breeding efforts focus on product development — goals set by scientists and researchers without accounting for the preferences of farmers. In practice, this can result in poor adoption of new varieties and unrealized potential.
“It is critical for breeders to be able to incorporate the diverse needs and preferences of end users into new varieties,” says Hale Ann Tufan, Survey Division Lead for NextGen Cassava. “Our trials in Nigeria and Uganda have revealed that there are significant differences in preferred traits between men and women, as well as various regional cassava processing methods. By understanding how descriptors for ‘good’ varieties, such as softness and texture, can be translated into phenotypes, we can develop methods to efficiently evaluate them along with traits such as disease resistance and climate resilience.”
Strengthening the capacity of national breeding programs will be critical in achieving self-sustaining breeding systems in sub-Saharan Africa. Over the next five years, NextGen researchers will continue to train the next generation of sub-Sahara African cassava breeders in modern plant breeding techniques like genomic selection and improved breeding methods.
International and regional partnerships are another important element of sustainability. NextGen researchers are reaching out to their counterparts in Ghana, Rwanda, Mozambique, Sierra Leone and the Democratic Republic of Congo to create a broader network of researchers who can work together to improve livelihoods and food security.
In Africa, NextGen collaborators include the International Institute of Tropical Agriculture and the National Root Crops Research Institute in Nigeria; the West Africa Centre for Crop Improvement in Ghana; the National Crops Resources Research Institute and Makerere University in Uganda; and the Tanzania Agricultural Research Institute in Tanzania. In South America, collaborators include Embrapa in Brazil and the International Center for Tropical Agriculture in Colombia. In the US, collaborators are Cornell University (who leads the project), the Boyce Thompson Institute at Cornell, the University of Hawaii, and the USDA-ARS in Ithaca.
For more information see www.nextgencassava.org