Hernán Ceballos, Clair Hershey, Carlos Iglesias & Xiaofei Zhang

Theoretical and Applied Genetics August 2021; vol. 134: 2335–2353

This paper reviews and analyzes key features from cassava breeding at the International Center for Tropical Agriculture (CIAT) over 50 years and draws lessons for public breeding efforts broadly. The breeding team, jointly with national program partners and the private processing sector, defined breeding objectives and guiding business plans. These have evolved through the decades and currently focus on four global product profiles. The recurrent selection method also evolved and included innovations such as estimation of phenotypic breeding values, increasing the number of locations in the first stage of agronomic evaluations, gradual reduction of the duration of breeding cycles (including rapid cycling for high-heritability traits), the development of protocols for the induction of flowering, and the introduction of genome-wide predictions. The impact of cassava breeding depends significantly on the type of target markets. When roots are used for large processing facilities for starch, animal feeding or ethanol production (such as in SE Asia), the adoption of improved varieties is nearly universal and productivity at the regional scale increases significantly. When markets and relevant infrastructure are weak or considerable proportion of the production goes for local artisanal processing and on-farm consumption, the impact has been lower. The potential of novel breeding tools needs to be properly assessed for the most effective allocation of resources. Finally, a brief summary of challenges and opportunities for the future of cassava breeding is presented. The paper describes multiple ways that public and private sector breeding programs can learn from each other to optimize success.

See: https://link.springer.com/article/10.1007/s00122-021-03852-9

Figure 1: The evolution of breeding schemes at CIAT. F1: seedling nursery; F1C1: cloned seedling nursery; SRT: single row trial; PYT, AYT and UYT: preliminary, advanced and uniform yield trials, respectively; GWP: genome-wide prediction; SIT: seed increase trial; TPY: training population yield trials; RM: rapid multiplication. Upward arrows indicate the duration of each breeding cycle (the orange arrow is for the rapid-cycling for high-carotenoids breeding).