By Kevin Pixley, International Maize and Wheat Improvement Center (CIMMYT)
The National Academy of Scientists just published a paper on a new multivitamin corn with “169 fold the normal beta-carotene” which “vastly exceeds” levels realized through conventional breeding. This achievement is exciting, and provides further proof of concept that transgenic approaches can result in greatly enhanced levels of micronutrients, but it hardly suggests that we should abandon conventional approaches.
While conventional breeding will most likely never allow us to reach the high levels possible with transgenics, in some crops, for some micronutrients, it can achieve the substantial and important increments necessary to improve human nutrition. In the case of maize, CIMMYT and other HarvestPlus partners are developing high provitamin A maize cultivars and have identified lines with 15 ug/g of provitamin A (which includes, and, is mostly beta-carotene).
This is far lower the 60 ug/g achieved transgenically as reported in this paper, but it is much higher than the 0 ug/g found in white maize, or 1.5 ug/g common in yellow maize. However, micronutrients are typically needed in very small amounts, and HarvestPlus nutritionists have concluded that 15 ug/g of provitamins A in maize grain is sufficient to have an important favorable nutritional impact on vitamin A deficient maize consumers.
In Zambia, where conventionally-bred provitamin A maize will first be released, HarvestPlus has estimated that up to 50% of the RDA for vitamin A could be met by eating 15 ug/g HarvestPlus orange maize instead of non-biofortified varieties. This suggests that increasing this amount by using transgenic approaches could meet 100% of the RDA. Additionally, other micronutrients not present in maize, could also be incorporated using transgenic approaches.
This may be true, but once a transgenic line is obtained (such as the one described in the paper), at least three expensive and time-consuming actions are required.
First, several years of conventional breeding are needed to assure that the transgenes are stably inherited and that they don’t result in inadvertent, undesirable associated effects.
Second, concurrent conventional breeding is needed to incorporate the transgenic line (or improved versions of it) into varieties that also perform well agronomically so that famers will want to grow them.
Third, there is an expensive and lengthy process of research to document and defend the human and environmental safety of transgenic crops, and to obtain the legal approvals to release and commercialize them.
Furthermore, in quite a number of countries there currently is no legal framework that allows commercial release of transgenic maize varieties. Thus, while transgenic approaches are clearly the fastest way to “prove the concept” that biofortified crops, and in this case, multi-micronutrient-biofortified crops are possible, they may not be the quickest to obtain usable products and desired impact. At the end of the day, the tortoise may still win the race.
