As we understand, transgenic approaches to bio-fortify or enhance the yields of crops grown primarily by subsistence farmers have been rather limited. This is particularly true for the starchy root crop cassava. Cassava is the primary source of calories for approximately 600 million people in the tropics and ranks fourth in caloric intake among all crops directly consumed by humans.1 Cassava is valued in many parts of the world for the food security it provides. It tolerates low soil fertility and drought and is resistant to many herbivores due to the presence of cyanogens.2 In addition, the roots of cassava can be left in the ground for several years prior to harvest, providing food security against famine.
Unlike many of the world's major food crop plants, cassava is not particularly amenable to genetic improvement through sexual crosses. Many cassava cultivars rarely flower and seed production is often low. In the field, cassava is clonally propagated by stem cuttings. This propagation method is ideal, however, for molecular approaches to cassava improvement, since each plant is clonally propagated and gene segregation or transfer through out-crossing is limited.
Transgenic Cassava with Enhanced Starch Production, to determine whether we could increase root starch production, we expressed a modified form of the bacterial gene encoding planting gene under the control of the root-specific in cassava potation promoter. This modified form of the enzyme lacks allosteric regulatory control and therefore would potentially be unaffected by the pool size of regulatory (negative) effectors. Previously, bacterial genes had been expressed in transgenic plants but with mixed outcomes.
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