Use of Transgene Expression to Elevate Micronutrients in Banana

Micronutrient deficiencies together constitute one of the major public health challenges worldwide and disproportionally affect populations in developing countries. The most important micronutrient deficiencies are vitamin A deficiency (VAD) and iron deficiency anemia (IDA) even though zinc, iodine and folic acid deficiencies are also very significant. Despite large investments in strategies such as food fortification and supplements to overcome these deficiencies, there is a large proportion of developing country populations who are “resistant” to these strategies. Biofortification, developing staple crops with enhanced levels of particularly pro-vitamin A (PVA) and iron, is a recent addition to strategies to alleviate micronutrient deficiencies in populations that depend on these crops as one of their staple foods. Golden Rice is certainly the most widely recognised biofortified product developed by genetic modification. VAD and IDA remain major public health problems in Asia and Africa where, for instance, India is the world’s largest banana producer and Uganda the highest per capita banana consumer. We have developed bananas which in the field in Australia have levels of PVA greater than 15 fold higher than wildtype through the over-expression of a single gene, phytoene synthase, using either constitutive promoters or fruit preferred promoters. We have expressed two different phytoene synthase genes, one from a naturally high PVA banana and also the maize gene used in Golden Rice 2. The two transgenes are differently expressed in bananas. We have now established a field trial in Uganda and have identified lines with elevated PVA.