Crop biofortification through genetic engineering : present status and future directions

Global food system is failing to deliver adequate quantities of healthy, nutritionally balanced food, especially to the resource-poor underprivileged people leading to micronutrient malnutrition. The malnutrition of minerals (Fe, Zn) and vitamin A are major food-related primary health problem among populations of the developing world including India where there is a heavy dependence on cereal-based diets and limited access to meat, fruits and vegetables. Vitamin A deficiency (VAD) alone is significant from the public health point of view resulting in over 330,000 child deaths every year, and about 57% of preschoolers and their mothers having subclinical VAD leading to increased morbidity and risk of mortality. While therapeutic supplementation of vitamin A is currently being addressed through sponsored nutrition programmes, they are not sufficient in covering the affected populations. Biofortification of important crop plants through biotechnological applications is a cost-effective and sustainable solution for alleviating VAD. Genetic engineering is the obvious alternative to enhance the β-carotene levels in crop plants. The development of the ‘golden rice’ proved that, it is possible to redirect a complete biosynthetic pathway of carotenoids by genetic engineering of multiple genes encoding key enzymes of the pathway. Recently, there have been several reports on the development of transgenic crops for enhanced levels provitamin A content in crops like maize, tomato, cassava, potato and mustered. At ICRISAT, transgenic events of groundnut and pigeonpea carrying either a single maize phytoene synthase 1 (psy1) gene or both psy1 and tomato β-lycopene cyclase (β-lyc) have been developed through Agrobacterium-mediated genetic transformation. Preliminary results showed a significant increase in the total carotenoids and β-carotene levels in the transgenic events. Provitamin A enrichment of these crops could have a significant impact on the nourishment and nutrient interactions by playing a major role in the bioavailability and metabolic efficiency in the affected populations