Target Crops

Cassava

Cassava as a vehicle for delivering pro-viamin A carotenoids

Cassava (Manihot esculenta Cranzt) is a perennial crop native to tropical America. Its starchy roots are one of the most important sources of food energy in many tropical countries (an estimated 70 million people obtain more that 500 cal/day from cassava). The crop produces reasonably well under marginal conditions of climate and soil and is frequently identified as a famine reserve due to its tolerance to drought and infertile soils, and its ability to recover from disease and pest attacks. It can also produce competitively in non-marginal areas. Cassava offers the advantage of a flexible harvesting date, allowing farmers to keep the roots in the ground until needed. Remarkably every part of the plant can be exploited: in addition to the roots the fresh foliage is also consumed in several regions of the world and the lignified stems are used as planting material. Because of its unique characteristics cassava grows in the marginal environments where poverty and malnourishment are also very prevalent.

During the 1993-95 period, about 16.5 million hectares were grown with cassava worldwide, producing 164 million tons of roots. For the period 1993 to 2020 annual growth of cassava production was estimated to range between 1.74 and 1.95% / year. The area of cassava under marginal environments has been continuously increasing, particularly for regions with poorer soils and lengthy dry seasons.

Research findings to date

In the past an emphasis was given to breeding cassava with white roots. However, considerable efforts were recently invested in measuring the variability for its carotenoids contents in roots and leaves from thousands of clones, along with other relevant information. It was found that high levels of carotenoids (more than 1 and 96 mg/100 g of fresh root or leaf tissue, respectively) could be found in certain clones. High levels of carotenoids were associated with yellow coloration, which facilitates the selection for high nutritional value. Clones with yellow roots, low cyanide level (a common characteristic in cassava) and excellent cooking quality have been identified.

Carotenoids levels in cassava roots were measured in different plants (same clone), different roots (same plant) and different sections of the same roots. The environmental effect on cassava was also measured. These studies allowed the conclusion that the high-carotene trait is fairly stable. Stability of carotenes upon different root processing methods was also measured. Boiling cassava roots will eliminate the cyanide present in them but will retain about 60% of the original levels of carotenoids. Furthermore, a detailed study of the quality of carotenoids in the roots revealed that more than 90% is ß-carotene. An important finding because this particular pigment has the largest capacity to be turned into vitamin A by the human body.

One interesting discovery was that the high-carotene trait seems to delay or reduce the onset of post-harvest physiological deterioration (PPD) of the roots. PPD is a natural process that spoils cassava roots one or two days after harvest. The short post-harvest storage life of cassava is a characteristic that limits the marketability of the roots and a delayed or reduced PPD would encourage farmers to grow yellow-rooted cassava clones.

Future Activities

The nutritional value of cassava foliage can also be exploited. In addition to the high levels of carotenoids, it has excellent amounts of protein and minerals. One problem that the carotenoids present in the foliage have, however, is the low bioavailability that increasing evidence is suggesting from green vegetables.

With the knowledge generated breeders in Africa, Asia and America redirected their objectives so that high carotenes is combined with good agronomic characteristics. A process that has already yielded promising results. Within five years elite cassava varieties with yellow roots will be introduced to target countries for their evaluation and eventual release. Simultaneously new crosses will be made to further increase the concentration of carotenes and/or improve relevant agronomic characteristic. Once a group of promising materials is identified an aggressive evaluation using the farmers’ participatory approach will be used for final evaluation, promotion and, hopefully, generalized adoption of these nutritionally improved varieties.

The activities are coordinated by the cassava breeder at CIAT (Hernán Ceballos) with key support from IITA for Africa (Dr. Alfred Dixon). Several national programs are involved (EMBRAPA, Brazil; CTCRI, India; Thai Ngyen University, Vietnam) as well as the contributions of non-government organizations such as Catholic Relief Service, Helen Keller International and World Vision.

For further information contact:
Hernán Ceballos (c/o CIAT)
International Center for Tropical Agriculture
Apdo Aéreo 6713, Cali, Colombia
Phone: (57-2) 445-0000
e-mail: h.ceballos@cgiar.org

HarvestPlus Publications

Cassava Brochure
English (176 KB)
Español (119 KB)

Publications on Cassava