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Wheat is one of the world's most important staple foods, especially in the form of bread. A by the Leibniz Institute for Food Systems Biology at the Technical University of Munich (LSB) and the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) now shows that extremely dwarf wheat has a less favorable gluten composition than semi-dwarf, dwarf, or tall wild type wheat, and therefore produces flour with poorer baking properties.

The work is published in the journal Food Science & Nutrition.

The introduction of so-called dwarfing genes (Reduced height-Rht genes) during the "Green Revolution" in the 1960s is considered a milestone in agriculture. These genes ensure that wheat plants are shorter and therefore less susceptible to wind damage (lodging). They can also invest more energy in grain filling, which has significantly increased yields.

"Today, more than 70% of all wheat varieties grown worldwide carry at least one of these genes," says co-author Andreas B枚rner, scientist of the Genebank Department at the IPK and co-author of the study.

Unclear influence on gluten

Until now, however, it was unclear whether the Rht genes not only alter the straw length but also the gluten composition in the grain. Wheat gluten consists of two storage protein groups: gliadins and glutenins. Gliadins make doughs stretchy and viscous and act as a softener. Glutenins give doughs elasticity and strength.

A balanced gliadin-glutenin ratio is crucial for good baking quality. If gliadins predominate too much, the dough becomes too soft, the bread volume decreases, and the baking result is poor.

To clarify the influence of the Rht genes on gluten composition, the research team compared tall wild-type wheat with five nearly identical variants in four wheat lines that differed only in the Rht genes. All lines were grown over three growing seasons at the IPK in Gatersleben to obtain comparable sample material. The climatic conditions of the 2021, 2022, and 2023 harvest years varied greatly.

The team came to the following conclusions:

The dwarfism genes found in modern wheat varieties (Rht1, Rht2, and their combination) had little effect on gluten composition. However, genes that cause extreme dwarfism (Rht3 and the combination Rht2+3) reduced the gluten content and shifted the gliadin-glutenin ratio, with potentially negative consequences for baking properties.

However, environmental conditions had an even greater impact on gluten composition than genes: warm and humid conditions in 2021 during the grain filling phase led to a particularly high and unfavorable gliadin-glutenin ratio.

"Our results show that the introduction of semi-dwarf and dwarf genes during the Green Revolution did not negatively affect the gluten composition of modern wheat varieties," explains first author and principal investigator Sabrina Geisslitz from the LSB.

She adds, "However, in the future, consideration should be given to whether genes that cause extreme dwarfism should be introduced into new breeds. Such genes could impair baking quality and also increase the immunoreactive potential, as both are associated with a high gliadin content."

"The study highlights how complex wheat breeding is," adds Katharina Scherf, head of the Food Biopolymer Chemistry research group at the LSB.

"As we were able to demonstrate, it is not only genes but also environmental conditions that determine the gluten composition in wheat. In view of climate change, this poses further challenges in optimizing breeds in terms of their gluten composition."

The "Green Revolution" refers to the worldwide introduction of modern agricultural technologies beginning in the 1960s. In addition to short-stature wheat, fertilizers, pesticides, irrigation, and mechanization contributed to a significant increase in yields, with ecological and social consequences that continue to this day.

Grain filling is the final growth phase of cereal plants, during which the pollinated ovaries develop into fully formed grains through the accumulation of starch and other nutrients from the plant's foliage. This process involves the transfer of carbohydrates and the accumulation of dry matter and water, which directly affects the final weight, size, and quality of the grains and thus the overall yield of the plant.

Gliadins and glutenins are two different groups of proteins that differ in their properties. Glutenins are giant macromolecules (polymers) consisting of many individual molecules that have aggregated. Glutenin polymers have molecular weights ranging from 500,000 to over 10 million and are among the largest naturally occurring proteins.

In contrast, gliadins are single molecules (monomers) with a molecular weight between 28,000 and 55,000. Research at the LSB has not only led to a better understanding of the function of gliadins and glutenins in baking. It has also helped to elucidate the structure of immunoreactive sequences of gliadins, which cause celiac disease in some people due to their genetic predisposition.

Celiac disease is a chronic disease of the small intestine. Gluten intolerance is the main trigger of the disease, which occurs particularly in people with a genetic predisposition. The other co-factors that stimulate the onset of the disease are not yet fully understood.