Abstract
This review highlights an integrative multidisciplinary eco-physiological, breeding and agronomical research on the tropical starchy root crop cassava conducted at CIAT. Laboratory and field studies have elucidated several physio-logical/biochemical mechanisms and plant traits underlying the high productivity in favorable conditions and tolerance to stressful environments, such as prolonged water stress and marginal low-fertility soils. Cassava is endowed with inherent high photosynthetic capacity expressed in near optimal environments that correlates with biological produc- tivity across environments and wide range of germplasm.Field-measured photosynthetic rates were also associated with root yield, particularly under prolonged drought. Extensive rooting systems and stomatal sensitivity to both atmospheric humidity and soil water shortages underlie tolerance to drought. The C4 phosphoenolpyruvate carboxylase (PEPC) was associated with photosynthesis and yield making it a selectable trait, along with leaf duration, particularly for stressful environments. Germplasm from the core collection was screened for tolerance to soils low in P and K, resulting in the identification of several accessions with good levels of tolerance. Cassava has a comparative advantage against major tropical food and energy crops in terms of biological productivity. Results also point to the importance of field research versus greenhouse or growth-chamber studies. In globally warming climate,the crop is predicted to play more role in tropical and subtropical agro-ecosystems. More research is needed under tropical field conditions to understand the interactive responses to elevated carbon dioxide, temperature, soil fertility, and plant water relations.
Highlights
Despite its domestication thousands of years ago by natives of the New World, until the early 20th century cassava was a neglected and less known crop outside the tropical and subtropical belt of Africa, Asia and Latin America, where it is commonly cultivated
Cassava is endowed with inherent high photosynthetic capacity expressed in near optimal environments that correlates with biological productivity across environments and wide range of germplasm.Field-measured photosynthetic rates were associated with root yield, under prolonged drought
The crop is widely grown as an annual staple food and animal feed by resource-poor smallholders mostly on marginal infertile soils without purchased production inputs in countries of tropical and sub-tropical Africa, Asia and Latin America, with a total cultivated area >20 million hectares producing over 240 million tons of fresh storage roots, more than 70% of it being in Africa and Asia, with the greatest share in the former [4,5]
Summary
Despite its domestication thousands of years ago by natives of the New World, until the early 20th century cassava was a neglected and less known crop outside the tropical and subtropical belt of Africa, Asia and Latin America, where it is commonly cultivated. The crop is widely grown as an annual staple food and animal feed by resource-poor smallholders mostly on marginal infertile soils without purchased production inputs in countries of tropical and sub-tropical Africa, Asia and Latin America, with a total cultivated area >20 million hectares producing over 240 million tons of fresh storage roots, more than 70% of it being in Africa and Asia, with the greatest share in the former [4,5]. Its often poorly-processed food products contain some anti-nutrient elements such as free HCN, phytates and polyphenols, and acetone cyanohydrin, which is commonly associated with an upper motor neuron disease known as “konzo syndrome” in some African countries [13,14,15] This occurs mainly with large intake of inadequately processed bitter-cassava products in areas hit by long drought and with shortages of balanced diets. Lity, reducing the many risks often encountered by the producers
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