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Valuable Straw – Biologists aim to identify new regulators of leaf growth in the barley genome

Prof. Dr. Michael Lenhard. Photo: Thomas Roese.

Prof. Dr. Michael Lenhard. Photo: Thomas Roese.

It is among the most widely cultivated crops in Europe. German farmers alone produce about 10 million tons of barley each year. Its straw used to be considered a low-value byproduct. More grain, less straw – for decades, this was the basic aim of barley breeding. The value of biomass, however, is increasing. What was once mainly used as animal bedding or insulation material is now being converted into energy. Farmers, too, could benefit from new barley varieties that produce more biomass. An international consortium, including Potsdam geneticists, is working on this idea.

The barley plants are already looking a bit worn. For three months, they have been standing in tall, narrow pots in a greenhouse in Golm and are starting to form rich tussocks. Brown leaves droop down among green ones. The typical barley heads with their long awns are already fully developed in most of the plants. Some of the plants are covered with small white bags – the sign of an ongoing crossbreeding experiment. The resulting seed is required for further experiments. Biologist Michael Lenhard, Professor of Genetics, examines a leaf between his fingers. Each of the 30 pots contains another type of barley with genetic material different from all the others, which leads to it having unique properties. Some stems are particularly long or short; others have many or only a few ears. The leaf size varies – and this is of particular interest to the geneticist.

Barley as an energy crop

Michael Lenhard and his team are part of a major research project that examines the potential of barley as an energy crop. “The point is to increase the biomass of plants,” explains the researcher. While the Potsdam researchers are studying leaf size, research groups from Italy, Spain, and Poland who are part of the joint project “BarPLUS” are researching ways of increasing photosynthesis, nitrogen use, and the number of side shoots to increase the biomass of barley plants.

The plants on Lenhard’s greenhouse table were bred decades ago, developed from mutations of the initial varieties’ genetic material. The researcher, therefore, refers to them as “mutants”. Now their genotype is to be the starting point for new varieties. The goal is a new barley ideotype with many grains but also more leaf mass, because biomass has for some time now been a valuable asset in the fields – as a source of biofuels or biogas. The high demand for this raw material has boosted rapeseed and corn cultivation. The disadvantage is that instead of potatoes, wheat, and beets, energy plants are increasingly being cultivated. Energy production and food production are in competition.

This might change with barley. The barely has hardly had the reputation of being a suitable energy plant. With good reason? “The composition of the straw in barley is particularly advantageous, because it contains a lot of carbohydrates,” explains Lenhard. In fact, the carbohydrate content is higher than in almost all other types of cereal, which is good for the energy yield. In order to breed a new variety that produces a lot of biomass at constant grain yield, the researcher is looking for those sections on the DNA that contain the information for leaf growth, specifically in terms of width: Wider leaves mean more biomass. 

Genetic analysis lays the groundwork for targeted plant cultivation

“The genomes of individual barley mutants differ in millions of positions,” says Lenhard. The barley genome is extensive and complex and, with just over 5 billion base pairs, is about one and a half times larger than the human genome. Searching for that section of the genome responsible for the broad leaves is like the famous search for a needle in a haystack. The researchers cross the broad-leaf mutants with a narrow-leafed variety, and their descendants are crossed again with each other. This results in narrow-leafed and broad-leafed plants. In an elaborate process, biologists first determine on which parental chromosome the desired genetic information could be by looking for genetic differences between the initial barley variety and the new crossings that form broader leaves. “We then try to identify the responsible position in the genome,” he explains. The researcher expects two years of work and about 2,000 to 3,000 plants per barley mutant before this will happen. “And that’s if all goes well.”

If the researchers succeed and are able to define which gene segment is responsible for the broad leaves, selective breeding will be able to transfer precisely this property to other varieties. “One would try to crossbreed this mutation into currently high-yielding varieties,” explains Lenhard. The number of crossing attempts will depend on where exactly the desired segment is in the genome. High grain yield but more biomass – that is the long-term goal. Knowing which DNA segment is responsible for the broad leaves will enormously facilitate the breeding process and save time and money.

In addition to the molecular and genetic analysis of barley, the project partners will examine other plant properties. What will happen when the different mutants and hybrids are grown in the fields? Will they survive this test and be able to deliver good yields under field conditions? One of the mutants has, for example, particularly broad leaves but the sheaths enclose the heads too closely. This limits fertilization and results in low yields. Many plant properties have to be tested to be able to achieve new varieties that are valuable to farmers. The researchers of the consortium estimate a 5-10% increase in biomass with the new barley varieties. Lenhard thinks that it will take about 10 years until a new variety of barley is in the fields. Until then, patience and perseverance are required. “And a bit of luck.” 


The Researcher

Prof. Michael Lenhard studied biology in Munich and Oxford. Since 2010, he has been Professor of Genetics at the University of Potsdam and studies the genetic and molecular basis of organ-size control in plants and its evolutionary modification.

Universität Potsdam
Institut für Biochemie und Biologie
Karl-Liebknecht-Str. 24–25, 14476 Potsdam
Email: michael.lenhard@uni-potsdam.nomorespam.de


The Project

“BarPlus” (Modifying canopy architecture and photosynthesis to maximize barley biomass and yield for different end-uses) explores methods for increasing biomass production in barley. The subproject at the University of Potsdam studies the genetic regulators of leaf size. Participants: University of Potsdam, Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria (Italy), University of Lleida (Spain), University of Silesia (Poland) Funding: European Union, Horizon 2020, FACCE-SURPLUS Duration: 2016-2019

Text: Heike Kampe
Translation: Susanne Voigt
Published online by: Daniela Großmann
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