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different soybean varieties growing in the field
PROGRESS IN PLANT BREEDING: Purdue researchers are identifying favorable traits in wild soybeans (far left) and moving them into crosses that resemble modern soybeans (far right).

Traits gleaned from wild soybeans move closer to market

New phytophthora resistance could come from wild ancestors.

The first time Jim Beatty saw wild soybeans growing at the Purdue University Agronomy Center for Research and Education, he seriously thought about calling a crew member to come mow them down. Fortunately, Beatty, superintendent of ACRE, figured out that what he thought were weeds were actually something else — ancient wild soybean plants. They were planted on purpose by one of Purdue’s leading plant researchers.

Don’t worry. Beatty wouldn’t begin to think about mowing the plants off today. He’s discovered they hold promise for higher soybean yields.

In Beatty’s defense, wild soybeans look nothing like modern soybeans. They grow close to the ground and produce small, hard seeds in pods that shatter easily. Purdue researcher Jianxin Ma recognized their good qualities. He just needs time to harvest the genetics of those favorable traits while leaving unfavorable traits behind.

“We’re making progress,” Ma says. And indeed, he and his team are making visible progress. Beatty first saw those scrawny, vining plants more than three years ago. Ma still grows some each year, but he also grows populations of soybeans that look much more like modern soybeans. Yet they contain genes discovered in wild soybeans.

Find useful traits
Ma has two large recombinant inbred line (RIL) populations of soybeans today made from crosses of wild soybeans with modern soybean lines. “We use the RIL populations to pinpoint several key genes,” he says.

Molecular markers and other sophisticated soybean breeding tools help Ma and his team track and map genes, and make desired crosses to introduce genes from the wild soybeans into the genetics of the modern soybeans.

The value of the wild population is the diverse genetic background they represent, Ma says. Plant breeders know that the secret to new discoveries of better resistance and improved quality traits relies on having a diverse population to select from in the beginning. “The genetic diversity of modern soybean gemplasm is fairly limited,” Ma says. “That’s why we took on the long-term project of growing wild soybeans and looking for valuable traits which are masked by the undesirable traits of those plants.”

Identifying favorable traits, understanding the genetics behind them, and moving the genes for those favorable traits into modern, useful lines is a relatively slow process. New tools like molecular markers make it easier, but it still takes time to arrive at a useful product — a modern line with an improved trait.

Tackle phytophthora
One track where Ma says they are making progress is in finding a new source of resistance to phytophthora root rot. Most current forms of resistance used in commercial lines are only partially effective or completely ineffective against new forms of the pathogen, Ma says. The fungus that causes phytophthora constantly evolves and produces new isolates. They’re often not controlled as well by existing genetic resistance as their ancestors were in the past.

Ma and his team have identified and mapped a “novel” gene that confers resistance to phytophthora. They’re in the process of moving it to modern soybean lines. In fact, one major commercial breeding program is already studying this trait.

Ma’s work is partially funded by the Indiana Soybean Alliance.

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