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Date: Aug 27, 2021

Rare barley mutation with potential Universities of Bonn and Bologna decipher cause of roots growing straight downwards

The importance of the root system for agricultural yields is often underestimated. Whether roots can access water and nutrients effectively also determines the resilience of important crops to drought and climate change. Researchers from the Universities of Bonn and Bologna (Italy) have discovered and described a mutant in barley: Its roots grow downwards much more sharply than usual. This discovery potentially provides a starting point for breeding more drought-resistant varieties. The study has now been published in PNAS.


Seven-day-old barley roots of mutant egt2: - It grows strictly downwards [hypergravitrop]. (© Photo: Gwendolyn Kirschner | INRES)


Barley is one of the most important cereals. Its uses range from brewing beer to groats, pearl barley, barley flakes and barley flour. Researchers led by Prof. Dr. Silvio Salvi of the University of Bologna discovered an unusual mutant of barley some time ago: Its roots do not spread sideways as they normally do, but grow straight down. The researchers termed this mutant "hypergravitropic", meaning that it follows gravity much more strongly than its conspecifics. The teams led by Prof. Dr. Frank Hochholdinger from the Institute of Crop Science and Resource Conservation (INRES) at the University of Bonn and Prof. Salvi, together with other colleagues, investigated the underlying causes.

The researchers compared the genome of the mutant with barley plants growing normally. They discovered a mutation on chromosome number five, which they named "enhanced gravitropism 2" (egt2), meaning "enhanced orientation to gravity". The "2" indicates that the team is also working on another study on a similar mutation (egt1). The researchers demonstrated that egt2 is indeed responsible for the vertical growth of the roots by artificially creating such a mutation in normal barley plants using the CRISPR/Cas9 gene scissors. "The result shows a similar appearance of the roots," reports lead author Dr. Gwendolyn K. Kirschner of the Institute of Crop Science and Resource Conservation (INRES) at the University of Bonn. "This allowed us to prove that we had identified the right gene."

Roots in the MRI scanner

The researchers grew the small barley plants in germination paper or soil and recorded the root angles using a scanner and special software. They also used resources from Forschungszentrum Jülich: There, the barley was grown in special "flower pots" that fit inside an MRI scanner. Using the magnetic resonance imaging technique, the researchers "looked through" the soil and recorded the growth of the roots in this way.

Plants with the egt2 mutation are far more sensitive to the influence of gravity than normal specimens. The researchers demonstrated this by placing the roots of the barley seedlings at a 90-degree angle to the direction of gravity. "This caused the roots of the mutants to grow significantly more in the direction of gravity than the comparative specimens without this mutation," says Dr. Kirschner. [...]


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