Sorghum's Quick Comeback

Sorghum's Quick Comeback

Researchers use Ethiopian genetics and new technology to boost yield

Renewed farmer interest in grain sorghum advanced acreage nearly 24% this year. The crop’s water thriftiness, price advantage compared to corn, flexibility in crop rotation as well as more forage and bioenergy opportunities are enticing to farmers. But sorghum lags behind other crops in technology and genetics. 

“Because of sorghum’s genetic diversity, it has a tremendous opportunity to bring more genetics online. As investment declined the past two decades, a lot of potential was left on the table,” says Justin Weinheimer,
Sorghum Checkoff crop improvement director. 

Sorghum Checkoff and USDA are working to identify new lines with improved drought tolerance and low- and high-temperature tolerance. “The work we’ve been doing for the past seven or eight years started off on cold tolerance and screening large numbers of the germplasm collections,” says John Burke, USDA-Agricultural Research Service scientist in Lubbock, Texas.

The team screened thousands of sorghum lines from China and Ethiopia. “In the Ethiopian lines, we found a whole new series of cold tolerant lines and selected the lines that performed well in our early season vigor tests,” Burke says. 

“We are doing the same thing with our drought tolerance research,” he adds. “The problem in screening for that trait is it is hard to find a reliable environment to test germplasm.” 

Sorghum has two classifications of drought tolerance: pre-flowering and post-flowering.

Sorghum plants with the multiseed trait (right) can produce up to twice the amount of seed weight compared with traditional plants (left). 

“We spent several years working on new techniques to screen plants under well water conditions—with no weather stress,” he says. “Through that research, we found a compound in sorghum called dhurrin. The higher the level of dhurrin in the plant, the greater post-flowering drought tolerance it has. Lines with low levels of dhurrin had pre-flowering drought tolerance. Using this, we are able to provide a relative measure of drought tolerance.” 

Some of the most exciting research comes from novel genetic mutations to find traits to enhance yield. USDA scientist Zhanguo Xin in the Lubbock group created a mutagenized population using sorghum’s first genome mapped line, BTX623, to find the multiseed trait. The mutant work brings novel genetics to the forefront—without the GMO stigma. 

Normally, sorghum produces more than twice the number of flowers as it sets to seed. Xin created a mutant that undid the metabolic process preventing the second flower from setting seed. With the multiseed trait, all of the flowers set seed, essentially doubling the plant’s grain production. 

Researchers have identified 30 multiseed lines and are working to pinpoint the genes that control this trait. So far, they have found two of at least seven genes that lead to increased seed production and are creating genetic markers for selection.

In the greenhouse, researchers observed potted multiseed plants produce twice the amount of seed weight compared with the parent BTX623 plant. “The problem we run into is when we put these plants into higher density populations, yield tends to fall back,” Burke explains. 

The team is focusing on moving the multiseed trait to another line less sensitive to crowding. “That way we are able to still get high yields at the planting rates farmers are used to,” Burke says. 

These advancements are still at least three to five years away from commercialization.

“Bringing in more genetics and molecular-based breeding is the next step in the evolution of sorghum. Fortunately, we can tap into technology that has already been developed, so the catch-up game will be much shorter,” Weinheimer says. 

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