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Alfalfa value focus of current round of biotech research

Since the commercial rollout of Round-Up Ready alfalfa in August 2005, a survey by the University of Wisconsin comparing conventional products with Roundup Ready varieties yielded a one-ton yield advantage (per acre) with Roundup Ready alfalfa.

“That's probably on the high side of what we're seeing. I would say the normal range is one-third ton to a one ton average increase across the country,” said Mark McCaslin, president of the Nampa, Idaho-based Forage Genetics International.

McCaslin knows Roundup Ready alfalfa. Forage Genetics is heavily involved in developing the technology's next chapter - a new generation of traits aimed at improving alfalfa value.

Forage Genetics, along with the U.S. Dairy Forage Research Center, and the Samuel Roberts Noble Foundation, launched a research venture called the Consortium for Alfalfa Improvement (CAI).

During the Western Alfalfa and Forage Conference in Reno, Nev., in mid-December, McCaslin explained the group's findings. He said new biotech traits research falls into two categories: output traits that enhance forage quality and input traits that improve the efficiency of crop production.

Formed in 2004, the CAI has explored two areas of alfalfa improvement: improved fiber digestibility and the increased efficiency of protein.

“Alfalfa is an important source of fiber in most dairy rations,” McCaslin noted. “Lignin is an anti-quality compound in alfalfa cell walls that increases with advanced plant maturity and reduces the digestibility of alfalfa fiber. There are various biotech tools that can be used to turn off or silence the native genes.”

Transgenic plants

Tools developed at the Noble Foundation have systematically shut down genes that code enzymes required for lignin synthesis in alfalfa. Meanwhile, the CAI scientists are evaluating transgenic plants with a reduced expression of lignin biosynthetic genes. While most transgenic plants contain reduced lignin content, McCaslin said most vary in lignin composition. Most transgenic plants have increased fiber digestibility, but agronomic performance varies greatly by transgene.

“Based on many lab and field studies conducted since 2000, we have learned transgenic plants with reduced expression of the fiber enzymes COMT and CCOMT have less lignin, improved fiber digestibility, and worth agronomic performance,” said McCaslin. Top alfalfa populations with the COMT or CCOMT transgene have been developed.

He said research hay in 2007 will be produced where the CAI dairy and sheep feeding studies should confirm improved animal digestibility of the reduced lignin alfalfa plants. Successful results would project the project into the development mode.

Reduced lignin alfalfa could offer growers a new genetic tool featuring increased harvest management flexibility plus increased forage quality and/or yield.

“By changing one gene, we're seeing a 10-15 percent increase in fiber digestibility. This is revolutionary in terms of a new genetic pool making significant quality improvements in alfalfa quality,” McCaslin noted.

Main challenge

The most important challenge in alfalfa to increase value is higher protein utilization. While alfalfa provides the most protein per acre of any U.S. crop, the protein is not efficiently utilized in dairy cows. The loss leads to increased nitrogen losses to the environment and supplemental protein feeding.

The alfalfa protein problem is due to post-harvest proteolysis (haylage) and the fast decline of protein in rumen (hay and haylage). The CAI is exploring two solutions: polyphenol oxidase (PPO) alfalfa and tannin alfalfa.

“Tannin alfalfa looks extremely promising. Alfalfa actually produces tannin in the seed coat but not in leafs and stems. We have model systems in forage that indicate if you produce tannins you get benefits.” He said a tannin solution could eliminate the need for protein supplements, a $1 billion cost to the dairy industry annually. “We want to capture the protein in the alfalfa plant versus having that paid out in supplements.”

McCaslin cited findings from the Dairy Forage Center stating that tannin alfalfa would reduce the need for protein supplements by 60 percent and yield up to a 12 percent net return to dairies.

McCaslin said a wide range of groups and institutions are focusing on improving crop performance traits. So far hundreds of value-added possibilities have been developed.

While more than half of the nation's alfalfa is grown with irrigation in dry areas of the country, transgenes with higher water use efficiency and drought tolerance are under the microscope. Working with Monsanto, Forage Genetics will test several potential drought resistance transgenic alfalfa plants in '07.

“We're focusing on drought tolerance, water use efficiency, increased biomass, and delayed flowering. Currently when alfalfa flowers, the rate of vegetative growth slows down so the yield accumulation slows down. Quality also decreases,” McCaslin said.

Genes for increased biomass or delayed flowering offer an exciting potential for alfalfa. Several such genes are now being inserted into alfalfa and offer a great opportunity to significantly increase the forage yield in alfalfa.

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