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Maize drop, ancient grains for crop immunity, heat stress hits wheat, biofortification hope

By Nicola Cottam

- Last updated on GMT

There's a 'food versus fuel' debate in maize but it still remains a staple food for many across the world despite increased use for biofuel production, researchers say
There's a 'food versus fuel' debate in maize but it still remains a staple food for many across the world despite increased use for biofuel production, researchers say

Related tags Wheat

Maize for food consumption is falling, ancient grains boost immunity to a deadly disease, short-term heat stress could threaten wheat output, and widespread biofortification of staple crops a distinct possibility.

Maize production bias towards ethanol and animal feed

In the last 10 years, the use of maize for fuel production has significantly increased, accounting for approximately 40% of production in the United States, a review finds.

The increased use of maize for biofuel production has sparked a ‘food versus fuel’ debate, the researchers said, because as larger quantities are eaten up in ethanol production, there is less available for human and animal consumption which could have a negative effect on prices.

Despite this, the researchers said maize remained a steady staple food for human consumption, particularly in Africa and the Americas.

Nutritionally, it is an important grain, they said. It contains 72% starch, 10% protein, and 4% fat and is a good source of B vitamins and essential minerals.

In countries with moderate to high levels of anaemia and iron deficiencies, cornmeal and maize flour is fortified with iron, minerals and vitamins to increase micronutrient intake and reduce illnesses.

The United States, China, and Brazil are the top three maize-producing countries in the world, with a combined output of around 563 out of the total 717 million metric tons produced per year.

Source: Annals of the New York Academy of Sciences
DOI: 10.1111/nyas.12396​  
“Global maize production, utilization, and consumption” 
Authors: P. Ranum, JP. Peña-Rosas, MN. Garcia-Casal

Ancient wheat key to fending off a killer fungus

Ancient wheat grains could provide the key to combating stem rust fungus (Ug99), which threatens up to 90% of the world’s wheat and barley production, a study finds.

Ug99 was first detected in Uganda in 1999 but since then a further six related pathogens have been discovered and are gradually spreading throughout eastern and southern Africa, Iran and Yemen. A major problem with the pathogen is that it is constantly evolving so genes that seem to offer immunity during one season become susceptible to newly developed varieties of the pathogen the following season.

Ug99 evolves so quickly that breeders will need an arsenal of resistant genes for use in commercial cultivars.

In a bid to find a solution, scientists at the Agricultural Research Service are analysing the genetic make-up of ancient wheat in an attempt to find genes with a resistance to Ug99. Einkorn and emmer wheat are two possible candidates, as well as goatgrass and triticale.

Goatgrass is a wild relative of domesticated wheat and is already being used to boost the resistance of commercial wheat to a number of other pests and pathogens. Conversely, the rye/wheat triticale has a natural resistance to Ug99 and researchers are confident that its genetic composition will help block transference of the pathogen to vulnerable wheat.

Several genes recently discovered by ARS researchers are already being used by breeding teams and are offering some Ug99 protection.

Source: Agricultural Research​, April 2014
“Looking to wheat’s wild ancestors to solve a modern problem”​ 
Authors: M. Rouse and Y. Jin

Damaging effects of short-term heat stress on wheat

Studies into the effects of heat stress on wheat yields tend to focus on extended periods of high temperature, but short periods of heat stress can also have a major impact of crop yields, researchers say.

Field and environment studies were conducted to analyse the effects of short-term heat stress in the Mediterranean on flag leaf senescence and crop yield.

The study focused on the response of wheat grain yield occurring at the green anther stage or early grain filling. It showed that heat treatments had significant adverse effects on grain yield and all wheat genotypes tested were significantly affected by heat stress during both years of the study period.

Seasonal differences on grain yield were identified and grain mass was shown to become less sensitive to heat stress at the later stages of grain filling.

Researchers observed a reduction in chlorophyll content in high temperatures for all genotypes, when averaged across years and heat stress. Genotypes with a higher rate of flag leaf senescence suffered greater yield loss (25%) than slower senescing genotypes, with losses of 10%.

Even though the heat treatments were imposed at the same physiological stage, genotypes that headed early in general yielded better under heat stress than genotypes (Janz) than those that headed later.

Overall, the results showed that the bread wheat genotypes CM9-6Y, CM9-4Y and Krichauff were more tolerant to heat stress and had slower senescence, a longer post-heading duration and better ability to tolerate heat stress than Janz, which was the most sensitive genotype investigated.

Source: Field Crops Research
“Effect of short-term heat stress prior to flowering and early grain set on the grain yield of wheat”
dx.doi.org/10.1016/j.fcr.2014.01.013​ 
Authors: ASMHM. Talukder, GK. McDonald and GS.Gill

A strong case for increasing micronutrient fortification

Increasing the bioavailability of micronutrients in crops is a viable solution to tackling nutrient deficiencies in developing countries, researchers suggest.

The bioavailability of micronutrients in unfortified staple crops such as maize, wheat, cassava and pearl millet is typically quite low in developing countries where nutrient deficiencies are commonplace.

In addition, antinutrients present in crops and food processing reduce the efficacy of inherent micronutrients. As such, international researchers are studying the effects of antinutrients and processing on micronutrients and the potential of bioforticiation to inhibit degradation and increase bioavailability.

Biofortification aims to improve the nutrient density of staple food crops through conventional plant breeding, agronomic management, or genetic engineering. This solution is particularly relevant now, the researchers said, as non-staple foods increase in price to further limit dietary diversity and food and nutrition security among the poor. They said biofortification is a practical strategy since it enables the population to grow and consume the same foods they are accustomed to eating while improving their micronutrient intake.

At the moment, the most common micronutrients targeted are iron, zinc, and provitamin A carotenoids. Studies have shown an increase in zinc absorption from biofortified wheat and millet, compared with standard crops, and that provitamin A carotenoids in biofortified maize efficiently convert to vitamin A.

There is therefore plenty of evidence, they said, to support efforts to breed plants with increased micronutrient concentrations in order to decrease the influence of inhibitors (and increase absorption) and offset losses from processing.

Source: Nutrition News
“Bioavailability of iron, zinc, and provitamin A carotenoids in biofortified staple crops”
DOI: 10.1111/nure.12108​ 
Authors: MR. La Frano, FF. de Moura, E. Boy, B. Lönnerdal and BJ. Burri

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