Researchers discover genes resistant to soybean pathogen

Jul 19, 2013

Purdue University researchers have identified two genes within the soybean genome that are highly resistant to a soilborne pathogen that causes Phytophthora root and stem rot, a disease that costs U.S. soybean growers more than $250 million annually in lost yield.

The discovery, made by a team of scientists led by Jianxin Ma and Teresa Hughes, could lead to the development of cultivars better able to withstand the pathogen Phytophthora sojae. The Purdue research was published online by Theoretical and Applied Genetics and is to appear in the journal's November print edition.

Naturally occurring Phytophthora sojae resistance exists in soybean germplasm. Most previous resistant genes, however, have lost their ability to fight off the pathogen, which has developed immunity to them. Together, the two newly identified genes appear stronger than most earlier genes and could remain viable for many more years, said Ma, a soybean in Purdue's Department of Agronomy.

"These two genes demonstrate resistance to all the predominant isolates of this pathogen found in Indiana and many other isolates that are virulent to previously identified ," he said. "If these two genes are effectively used in Indiana and other Midwest , an annual net increase in would be anticipated."

Phytophthora sojae has been a problem for Indiana soybean farmers since it was first found in the state in 1948. The pathogen thrives in wet, cool conditions and produces spores that move in water and onto soybean roots. Diseased roots form lesions that can move up the stem and kill the entire . The pathogen also produces spores that can remain dormant in soil through the winter and become active when warm weather returns.

Even in normal crop years Phytophthora sojae is responsible for 8-15 percent crop loss nationwide.

Because the soybean plant's own to Phytophthora sojae has proven to be the best way to control the pathogen, the mapping of the in recent years has improved the odds of finding other resistant genes. But the Purdue team made its discovery looking for a genetic answer to another soybean problem, said Hughes, a U.S. Department of Agriculture plant pathologist and adjunct professor in Purdue's Department of Botany and Plant Pathology.

"We were originally looking for possible resistance to Asian soybean rust," she said. "Our experimental locations had high Phytophthora pressure, and we found that these genes did very well against that disease. That was our first clue that they might have good resistance to Phytophthora sojae."

During its three years of study the Purdue researchers have developed molecular "markers" - identifying tags - that can be used to expedite the transfer of the resistant genes to soybean cultivars. That process is known as marker-assisted selection.

"There are about 46,000 predicted gene models in what we call the reference soybean genome," Ma said. "These markers allow rapid pyramiding of multiple resistant genes into a single cultivar in order to boost the effectiveness of resistance."

Although Phytophthora sojae eventually could render the two resistant genes ineffective, the pathogen itself likely would become much weaker, Hughes said.

"Every time a pathogen overcomes resistance in its plant host it has to give up something itself," she said. "So if it turns out that in order for the pathogen to overcome this new resistance it ends up having a fitness penalty - for instance, it can't compete as well or it doesn't survive as long in the soil - then these genes will last longer.

"We believe these genes are durable, but we don't know enough about them yet to predict how effective they could be, and for how long."

Ma, Hughes and collaborating Purdue researchers Scott Abney, Feng Lin, Meixia Zhao, Jieqing Ping, Austin Johnson and Biao Zhang plan to continue their research. They next hope to move their work from greenhouses and into field trials. After that the resistant lines could make their way into commercial cultivars.

"This has the potential to provide a higher profit margin for soybean farmers, as well as reducing the use of harmful chemicals and promoting a cleaner environment," Ma said.

Explore further: Irish potato famine-causing pathogen even more virulent now

More information: link.springer.com/content/pdf/10.1007%2Fs00122-013-2127-4.pdf

add to favorites email to friend print save as pdf

Related Stories

Mystery of nematode pest-resistant soybeans cracked

Oct 15, 2012

For 50 years, the world's soybean crop has depended on the use of cyst nematode resistant varieties of beans, but no one knew how these plants fought off the nematode pests. Now, the secrets of resistant soybean plants are ...

Recommended for you

Genetic code of the deadly tsetse fly unraveled

11 hours ago

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Engineered E. coli produces high levels of D-ribose

12 hours ago

D-ribose is a commercially important sugar used as a sweetener, a nutritional supplement, and as a starting compound for synthesizing riboflavin and several antiviral drugs. Genetic engineering of Escherichia co ...

User comments : 0

More news stories

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Ocean microbes display remarkable genetic diversity

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...

Cell resiliency surprises scientists

New research shows that cells are more resilient in taking care of their DNA than scientists originally thought. Even when missing critical components, cells can adapt and make copies of their DNA in an alternative ...