Sierra Mixe Maize: This Unique Corn Variety from Mexico May Cut Fertilisers Use

When researchers first saw the Sierra Mixe maize, they were amazed by its ability to grow up to 16 feet without the use of fertilizers. According to a 2018 article in The Atlantic, scientists from the University of California, Davis, spent years researching before discovering that the secret to this endemic maize's growth was its aerial roots.

Nitrogen is required for the growth of almost all plants. With the help of microbes found in their roots, they convert atmospheric nitrogen into usable ammonia. Cereal crops, such as rice and maize, have a limited number of nitrogen-fixing bacteria in their roots. To stimulate growth, farmers use nitrogen-rich fertilizers in the soil.

According to British journalist Ed Yong, it was discovered in the case of Sierra Mixe maize that the bacteria-rich aerial roots, which resemble a group of mucus-covered red tubes, were directly converting nitrogen from the air into a nutritional form. This direct nitrogen conversion did not necessitate the use of artificial fertilizers in the crop by the locals.

This maize variety is not suitable for the fast-paced world of commercial farming because it takes up to eight months to fully mature. Many biochemists believe that if a method can be developed to accelerate the growth of Sierra Mixe maize without compromising its aerial roots, the world will have a fertilizer-free maize variety.

Scientists have spent years attempting to develop nitrogen-fixing cereal crops through genetic engineering, with little success. However, now that we know that at least one type of corn can fix nitrogen naturally, the ability could potentially be transferred into conventional varieties via classical crossbreeding, mucus transplants, or both. These methods may make the final product more acceptable to the public than a genetically modified crop.

Michael Kantar, a botanist at the University of Hawai'i at Mnoa, cautions that it is too early to say whether the results will have a significant impact on food security because the team has yet to demonstrate that the resulting corn can fix enough nitrogen to grow at commercially useful scales. It's also unclear whether the genes responsible for the ability have any drawbacks. "However, if these questions can be answered," he says, "this may provide a way to significantly reduce fertilizer use worldwide, which would have hugely beneficial environmental effects."