Biofortification could help enhance sorghum nutrition

According to Google, biofortification a process to nutritionally enhance food crops with increased bioavailability to humans developed and grown using conventional plant breeding, agronomic practices or modern biotechnology techniques.

Davina Rhodes, an assistant professor of nutritional genomics at the Rhodes Lab at Colorado State University, is working to help feed the malnourished across the globe with the help of sorghum.

The lab’s mission is to reduce vitamin A deficiency through crop biofortification. According to its website, research is focused on understanding the genetics of carotenoid variation to help breeders develop high provitamin A staple crops. The lab uses tools like crop genetics, human nutrition, and analytical chemistry to strategize and carry out crop biofortification, focusing primarily on sorghum.

Rhodes was a speaker during a Center for Sorghum Improvement seminar held in late 2022. The registered dietician said there are about 2 billion people who are overweight or obese, leading to a number of chronic disorders. There are another 2 billion people that are micronutrient deficient.

“This can lead to infectious diseases, stunted growth, wasting, among other things,” she said. “I’m a nutritionist by training and I used to work as a dietitian in the hospital. I worked mostly with patients who had Type 2 diabetes and after a couple of years of doing that, I came to realize that what I really wanted to do was work on solutions that prevented nutrition related disorders, rather than treating them after they’ve already manifested.”

Rhodes said it’s harder to help people once they get to the hospital, as they’re already so sick. Inspired by Norman Borlaug’s words, “food is the moral right of all who were born into this world,” she turned to science and technology to help her with her goals.

Her work is most closely focused on sorghum, but Rhodes also works on cereal grains as they provide the majority of nutrients needed in the human diet. In some parts of the world, 80% of humans’ diet comes from grains.

“So changes in cereal grain nutrients can have a big impact on human nutrition and on the negative health effects of both under nutrition and over nutrition,” she said. “I mostly work on sorghum and I also mostly work on carotenoids in sorghum because carotenoids keep us alive, both plants and animals.”

Some carotenoids are called provitamin A carotenoids and are converted into vitamin A when consumed. Vitamin A is an essential nutrient that can only be acquired through diet—from either animal sources or plant sources. It’s also essential for immune function for growth and development, as well as reproduction and vision.

“And then there are non-provitamin A carotenoids and those play an important role in health as well,” she said. “Especially in protecting against age-related macular degeneration in the eye.”

In plants, carotenoids act as antioxidants and photo protectors which are involved in photosynthesis. In the seed, they’re fairly low in concentration, maybe even absent in the endosperm of major cereal grains.

“But carotenoid production in the seed is important for maturation and dormancy. They’re precursors for plant hormones that control these activities,” she said. “They also have antioxidant activity in the seeds so they can help produce membrane deterioration.”

Development

Rhodes said there’s a need to develop high carotenoid sorghums that can be grown in areas where vitamin A deficiency is prevalent and where sorghum is already a stable crop.

“Vitamin A deficiency is a tragic deficiency. It’s the leading cause of preventable blindness in children under the age of 5,” she said. “It increases the risk of death from common illnesses, and it’s found in the poorest communities in the world. So it’s a key marker of poverty and inequality.”

Rhodes said there are four complementary strategies in the workflow to improve the nutrition of the population—supplementation, fortification, dietary diversification and then biofortification. Supplementation delivers a manufactured nutrient, while fortification adds a nutrient to the food during processing. dietary diversification is consuming a variety of foods and biofortification develops nutrient dense food crops.

“I’m working on biofortification in sorghum using traditional breeding,” she said. “Some people ask, why not just use supplementation, diversify, or fortify? There are a lot of factors that can prevent people from using those programs.”

There are factors like geographic barriers, and with some people living in rural areas far from clinics, that provide a need for supplementation programs.

Breeding methods tend to have a higher acceptance rate by the end users, while those techniques that utilize biotechnology or genetic engineering tend to have a very low acceptance rate.

Agronomic biofortification is where fertilizer is applied to the soil or leaves, and this is often more of a short-term solution or can be used when the other methods aren’t applicable. But it’s also expensive. Rhodes’ method has the highest acceptance for the users.

In the development phase is where the breeding, modifying, or managing takes place. It means carrying out different types of biofortification.

“You also study and breed for nutrient retention and bioavailability and carry out clinical efficacy studies to see if the biofortified crop is actually improving nutrition status,” she said.

When the delivery phase is reached, the biofortified lines are released and disseminated. This is where results are scaled up to reach more people and work with local and international groups to find ways to ensure long-term sustainability of the biofortified crops.

Her results

Rhodes said in the discovery phase, they identified five priority populations around the globe as their potential top priorities. These were based on several factors—primarily looking at countries that already have high sorghum consumption, coupled with high rates of vitamin A deficiencies.

During this phase, they screen the germ plasm to get a sense of what there is to work with. This tells Rhodes and her team if biofortification through breeding is even possible. If there’s no variation in the germ plasm, then breeding isn’t going to do anything and they’ll have to rework plans.

There are three major carotenoids found in sorghum, according to Rhodes. Beta carotene is the only one that gets converted to vitamin A.

“That was one of the most important to us, but it’s also lowest concentration,” Rhodes said. “What we found is that there is a range of concentrations in the germ plasm and so that supports our hypothesis that maybe breeding will actually work to increase carotenoids.”

Rhodes said researchers wanted to get a sense of where the high carotenoid lines come from and what their genetic relationships are. They evaluated concentrations by country and looked at the lines in which they actually measured the carotenoids through high-performance liquid chromatography. In those lines they couldn’t measure, they predicted the levels.

They also looked at the genetic relationships between the lines.

“We found that they do tend to cluster by country, meaning the ones from the same country are more genetically similar to each other, which is unsurprising,” she said. “We also saw that there is diversity within those countries as well a little bit of diversity between the countries and so we have some genetic diversity to work with for breeding.”

One of the goals for breeding biofortification is to breed for high carotenoid alleles without antagonistic pleiotropic effects.

“We need to know if we mess with one gene in the seed is it going to change or affect other important traits throughout the plant?” Rhodes said.

Next steps

Rhodes said the next step is to start breeding for the high carotenoids. They hypothesized that high carotenoid parents have complementary alleles making it possible to increase the concentrations through breeding. To test they crossed high carotenoid by high carotenoid lines.

Their data is suggesting parents have complementary high carotenoid alleles.

“That allow us to breed for higher concentrations of carotenoids,” she said.

The future of their project has a lot to do with international applications. She has sent some of the high carotenoid lines they developed to Haiti, where a breeder is going to be crossing those lines with his breeding lines to see if they can develop high carotenoid lines in an actual breeding program.

Eventually Rhodes will be phenotyping the crosses and will evaluate them once back in the lab. They’ll plant the highest ranking progeny and cross them again. They’ll pay special attention to those with markers for sugarcane aphid resistance.

“What we’re hoping at the end of this is to have tropically adapted sugarcane aphid resistant carotenoid biofortified lines that can be deployed to breeding programs and regions like Sub Saharan Africa,” she said. “We’ve already sent down about 30 lines and they’ve planted them and unfortunately, I think only about 10 of them germinated.”

Rhodes isn’t sure if the seed had something wrong with it or if the germination issues with high carotenoid sorghum seed related to a specific acid production or something else. But that’s something they’ll continue to work on she said.

For more information about Rhodes’ work visit biofortificationlab.org/.

Kylene Scott can be reached at 620-227-1804 or [email protected].