Scientists release new low-lignin sorghums: ideal for biofuel and feed

New, low-lignin sorghum germplasm lines developed by researchers at the U.S. Department of Agriculture's Agricultural Research Service (ARS) and collaborating university scientists are now available for bolstering the grain crop's value as both a livestock feed and ethanol resource.

Lignin is a cellular 'glue' of sorts that imparts rigidity and strength to plant tissues. It also plays direct and indirect roles in helping plants fend off insects and pathogens. But breeding sorghum with reduced lignin can have beneficial effects, too, say plant pathologist Deanna L. Funnell, geneticist Jeffery F. Pedersen, and agronomist John J. Toy at ARS’s Grain, Forage, and Bioenergy Research Unit in Lincoln, Nebraska.

Atlas bmr-12, which was developed by the ARS team and evaluated with University of Nebraska-Lincoln colleagues Richard Grant and Amanda Oliver, is a good example of reduced-lignin’s benefits. In the laboratory, Atlas bmr-12 scored higher on fiber digestibility than standard sorghum, which should result in higher milk production and higher beef gains when cattle are fed the new variety. Atlas bmr-12’s greater fiber digestibility also raises the prospect of improved sorghum-to-ethanol conversion at the processing plants.

The researchers initially anticipated that breeding low-lignin sorghum would diminish the plants’ defensive capabilities. But they observed otherwise in tests with harmful species of Alternaria and Fusarium fungi.

In the lab, Funnell inoculated low-lignin lines—containing either bmr-6 or bmr-12 genes—and control varieties with Fusarium moniliforme and compared the length of the red-pigmented lesions that demarcate the fungus’s spread. Inside the stems, or peduncles, of the low-lignin lines, the lesions were shorter than those of the controls, suggesting bmr-6 and bmr-12’s greater resistance. On bmr-12, for example, the lesions averaged 78 millimeters long, versus 117 millimeters for the control:
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“This surprised us because lignin has been linked to disease resistance,” says Funnell. During breeding stages, Pedersen incorporated two of several genes for a trait called “brown midrib,” which is associated with reduced lignin. The researchers theorize that the genes may have disrupted the functioning of key enzymes so as to allow buildup of phenolic compounds with antifungal activity.

“We hypothesize that there’s a difference in the levels of phenolics—the precursors to lignin—and some of these have been shown to be toxic to fungi,” says Funnell. The phenolics pose no such danger to livestock or humans and may confer health benefits.

ARS has received U.S. Plant Variety Protection on Atlas bmr-12.

Sorghum has become one of the most interesting and most researched energy crops amongst bioenergy scientists. Several projects are underway to develop drought-tolerant varieties, high sugar varieties and high biomass varieties. Some sorghums promise great opportunities for use in developing countries, where they can be grown with low inputs to yield both fuel, food, fiber and fodder (earlier post and more here).

Last month, a major breakthrough was achieved when researchers succeeded in engineering a sorghum that can grown in soils plagued by aluminum toxicity. Such acidic soils limit crop production in as much as half the world's arable land (previous post).

Photo: Geneticist Jeff Pedersen (left), plant pathologist Deanna Funnell, and agronomist John Toy examine a field of Atlas bmr-12 sorghum that will be used in digestibility studies. Courtesy: Stephen Ausmus.

References:
U.S. Department of Agriculture, Agricultural Research Service: Scientists Release New
Sorghum for Feed and Fuel - September 10, 2007.

U.S. Department of Agriculture, Agricultural Research Service: New Sorghum is Ideal for Both Fuel and Feed - September 10, 2007.

Biopact: Major breakthrough: researchers engineer sorghum that beats aluminum toxicity - August 27, 2007

Biopact: Sun Grant Initiative funds 17 bioenergy research projects - August 20, 2007

Biopact: Researchers and producers optimistic about sweet sorghum as biofuel feedstock - July 27, 2007

Biopact: Mapping sorghum's genome to create robust biomass crops - June 24, 2007

Biopact: Joint Genome Institute announces 2008 genome sequencing targets with focus on bioenergy and carbon cycle - June 12, 2007