Stories Barley, Beer, and Biotechnology: Field trials with GM barley underway in Germany

Barley is grown around the world and has been used for food and beer making since ancient times. Efforts to keep improving barley by conventional breeding, however, have been met with limited success, making it a good candidate for genetic engineering. Transgenic barley lines with immunity to a virus, resistance to fungal root rot, and improved brewing properties have been developed over the past several years. Now, field trials at the University of Giessen and the Friedrich-Alexander University Erlangen-Nuremberg in Germany are testing some of these lines for potential unintended effects.

The field trials in Germany are taking a closer look at properties of two transgenic barley lines. One line produces an enzyme that can break down the cell walls of pathogenic fungi, and the other line produces a modified enzyme that improves the quality of malt for beer making.

Ripening barley grains     Root rot damage: Rhizoctonia patch in spring barley

GM barley with extra defences against root rotting fungi The plough may be almost as old as agriculture itself, but progressive-minded farmers in many parts of the world are finding success without it. Tilling damages the soil’s delicate crumb-like structure, disturbs beneficial fungi, reduces soil organic matter, compacts deep soil layers, and causes erosion. Like most things, however, no-till agriculture also has its drawbacks. Although it leaves beneficial fungi undisturbed, it also makes a better environment for root rotting fungi. The pathogenic fungi Rhizoctonia solani and Rhizoctonia oryzae have been becoming more and more widespread in areas where no-till systems are in place, especially the northwest United States and southern Australia. One of the major problems with fungal root rot is that it can significantly reduce yield without causing any conspicuous above-ground damage.

Farmers have spent decades trying to come up with effective ways of managing Rhizoctonia. Fungicides are an option, but treating soil with fungicides is much more complicated than simply spraying the leaves, and it also takes a toll on the environment. For all practical purposes, managing Rhizoctonia with fungicides is prohibitively expensive.

Crop rotation can sometimes help by depriving the fungus of its host and starving out the pathogen, but in this case, Rhizoctonia infects a wide range of plants. Most rotation schemes would do nothing to cut back the occurrence of root rot. Rotating barley with an appropriate non-crop plant could help, but it would mean that farmers would have to go a year without income.

Plant breeders have tried for years to improve barley’s disease resistance with conventional breeding. To date, searches for genetic material for breeding programmes have been inconclusive and disappointing. Barley has a relatively small genetic base of possible breeding partners, and among these, there are no varieties with good resistance to Rhizoctonia.

One interesting way of managing Rhizoctonia is using a biological approach. In essence, using fungi to fight fungi. Trichoderma harzianum attacks other types of fungi, including Rhizoctonia, and feeds on their cells. The cocktail of substances Trichoderma uses to digest its host includes an enzyme called chitinase, which breaks down a substance known as chitin. Chitin is an essential component in fungal cell walls. There are different forms of chitin, and correspondingly, there are many different forms of chitinase. Barley itself already contains several chitinases, but none are effective against Rhizoctonia. Scientists at the University of Washington in the USA reported in 2003 that they successfully inserted a chitinase gene from Trichoderma into the barley genome. The resulting plants had a high level of resistance to Rhizoctonia.

Undergoing field tests: Transgenic barley designed to improve beer brewing.

Transgenic barley for better beer making Beer making is an ancient process that traditionally uses only three ingredients: water, malted barley, and hops. The malt is the carbohydrate source, and the hops add flavour and act as a preservative. The beer purity act decreed in Bavaria in 1516 is still observed by German breweries today and restricts brewers to these three ingredients. Another important ingredient in beer is yeast. Although not originally added in the beer making process, it was always present and is responsible for converting sugars to alcohol. Beer makers now use yeast cultures custom tailored to specific types of beer.

Malt: Partially germinated barley grains packed with sugar

To make malt, grains are bathed in warm water, which causes them to start germinating. When the grains begin to grow, they produce enzymes that make their energy stores available by breaking down their starch reserves into simple sugar molecules. At this point, the germinating grains are killed by heating, but they remain loaded with sugar. The dried, germinated grains are known as malt. To make beer, malt is flushed with hot water to dissolve out the sugars, and the resulting sweet liquid is fermented by yeast into a slightly alcoholic, carbonated drink.

Although maize and wheat can be used to make beer, beer is traditionally made with barley. One of the original reasons barley was used for beer making was to leave the other more valuable grains, like wheat and rye, for food. In addition, barley has a higher content of the enzymes essential for breaking down starch and releasing sugar.

The longer the malting process, the more time enzymes have to produce sugar. But when the malting goes on for too long, the seedlings start using up the sugars for their own growth. That’s why the process is halted at the optimal point by drying out the sprouting grains. The heating process that kills the grain also deactivates the enzymes. Therefore, whatever starch and cell material is leftover when the grains are heated and dried cannot be used. Non-degraded endosperm cells can lead to problems for brewers including unwanted viscosity and clogged filters.

Modern biotechnology has already stepped in to address these issues. Genes for the enzymes amylase, which breaks down starch, and glucanase, which breaks down endosperm cell walls, have been spliced into microorganisms and are produced on a large scale. Most beer makers purchase enzyme supplements to optimise brewing.

But what if the barley’s own enzymes could remain active in spite of the heating process? It would make for better brewing without the need for enzyme supplements. This is exactly what researchers at the Carlsberg brewery in Copenhagen and at Washington State University in the US set out to do. They took glucanase genes from bacteria and identified the most heat stable forms. Then they engineered a heat stable glucanase gene and expressed it in barley. The resulting enzyme remained active after four hours of heating. Barley’s own glucanase enzymes are destroyed after only four minutes of heating.

Enhancing glucanase activity in barley also improves its quality as feed for livestock. When poultry are fed barley, they have poor growth rates. This is because poultry are deficient in glucanases and cannot fully break down endosperm cell walls. Feeding studies have shown that poultry fed genetically modified barley with heat stable glucanase outperformed poultry that were fed conventional barley.

Field trials in Germany

The field trials now underway in Germany are taking Rhizoctonia resistant barley and barley with heat-stable glucanase and are looking closely for potential unexpected effects. Researchers will be studying the barley lines’ gene expression profiles to see if there are any unexpected shifts in gene expression. They will also check to make sure there are no unexpected changes in grain quality. The anti-fungal activity of chitinase and the incidental anti-fungal activity of glucanase will be checked to see if they also block interactions with beneficial fungi. The research projects will end in 2008, but preliminary results are expected this year. See the upper part of the column on the ride side of the page for links to further information on these field trials.

See also on GMO-Compass:

• Breeding Aims: Disease Resistance
• Grocery shopping: Juice, Soft Drinks, Wine, and Beer