Rapid Cycling Recurrent Selection for Increased Carotenoids Content in Cassava Roots

Improving total carotenoids content (TCC) in cassava roots is an important strategy to reduce vitamin A deficiency in human populations that rely on cassava as a source of energy in their diets. The high heritability for TCC in the roots allowed the International Center for Tropical Agriculture to implement a rapid cycling recurrent selection approach that reduced the standard length of each cycle from the ordinary 8 yr to 3. Data from successive evaluation nurseries suggested that gains have been made through time. However, no comparison of different cycles of selection has been made when representatives of each cycle were grown together. This study compares 4 to 5 clones representative of cycles of selection from 2004 to 2009. Results demonstrated significant gains for TCC as well as for total beta-carotene (TBC) expressed both in a fresh and dry weight basis. Although dry matter content (DMC) was not a selection criterion during the selection process, it increased with the successive cycles of selection. This suggests that indeed, simultaneous gains for TCC, TBC, and DMC are feasible. This finding is relevant for the important ongoing efforts at the International Institute of Tropical Agriculture and African National Programs to release biofortified cassava clones in Africa with adequate levels of dry matter content.