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Crop roundup: sudden death syndrome

Iowa State University researchers take steps toward improved SDS resistance, a new discovery could lead to herbicides and fertilizers working naturally with plants, Bayer CropScience gives €1 million (EUR) to support physical mapping of several wheat chromosomes, and split nitrogen applications could save you money.

ISU researchers sequence genome of a soybean fungus responsible for sudden death syndrome
Researchers at Iowa State University have generated a draft genome sequence of Fusarium virguliforme, a pathogen that causes sudden death syndrome (SDS) in soybeans.
 
Using this draft genome sequence, the scientists have identified candidate genes required for causing SDS in soybeans and also the genes unique to this pathogen.  The sequencing was funded by the Iowa Soybean Association and the Soybean Research Development Council.
 
Madan Bhattacharyya, an associate professor of agronomy leading the research team, said the genome sequence generated for the research community will expedite efforts towards discovering mechanisms this pathogen uses to cause disease, and will ultimately lead to soybeans with improved SDS resistance.
 
“We’ve just drawn the roadmap so that researchers can do their work in an efficient way. This is a resource for them to avoid doing all the hard experiments that took us more than six months. Now we can do the same work in less than a week,” Bhattacharyya said. “There is so much known about pathogens similar to our SDS pathogen, we can use that information to quickly determine if it is applicable to our pathogen.”
 
Bhattacharyya says future plans include creating a gene for the development of a soybean resistant to SDS. They also have started to incorporate resistance genes from another plant species into soybean plants for enhancing SDS resistance. And they will explore if soybean can genetically be modified to suppress the growth of the SDS pathogen in infected roots. The work has been funded by a $5.35 million Agriculture and Food Research Initiative (AFRI) grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture (USDA-NIFA) that started in January 2013.
 
“Our goal has been to produce SDS-resistant soybean plants. Thanks to the funding from USDA-NIFA, and also from Iowa Soybean Association; we have a golden opportunity to accomplish our longer-term goal. We are beginning our second year of the grants from both agencies and already we’ve made a lot of progress,” he said.
 
“Because the genetic and biochemical interactions between pathogens and their host plants are complex and constantly evolving, a thorough understanding of the pathogen genome is essential for developing durable defense strategies to protect plants against these disease pathogens,” said Ed Anderson, senior director of supply and production systems at the Iowa Soybean Association.
 
Newly discovered receptors in plants help them recover from environmental changes, pests, and plant wounds

ATP (adenosine triphosphate) is the main energy source inside a cell and is considered to be the high energy molecule that drives all life processes in animals and humans. Outside the cell, membrane receptors that attract ATP drive muscle control, neurotransmission, inflammation and development.  Now, researchers at the University of Missouri have found the same receptor in plants and believe it to be a vital component in the way plants respond to dangers, including pests, environmental changes and plant wounds. This discovery could lead to herbicides, fertilizers and insect repellants that naturally work with plants to make them stronger.

“Plants don’t have ears to hear, fingers to feel or eyes to see,” said Gary Stacey an investigator in the MU Bond Life Sciences Center and professor of plant sciences in the College of Agriculture, Food and Natural Resources. “Plants use these chemical signals to determine if they are being preyed upon or if an environmental change is occurring that could be detrimental to the plant. We have evidence that when ATP is outside of the cell it is probably a central signal that controls the plant’s ability to respond to a whole variety of stresses.”

Stacey and fellow researchers, graduate student Jeongmin Choi and postdoctoral fellow Kiwamu Tanaka, screened 50,000 plants over two years to identify the ATP receptors. By isolating a key gene in the remaining plants, scientists found the receptor that aids in plant development and helps repair a plant during major events.

“We believe that when a plant is wounded, ATP is released into the wound and triggers the gene expressions necessary for repair,” Stacey said. “We think ATP is central to this kind of wound response and probably plays a role in development and a whole host of other plant responses to environmental changes and pests. We believe that with further study, researchers may be able to identify ways to naturally work with a plant’s own processes to protect it from major environmental events, plant wounds and insects.”

Future research will focus on how this receptor works with ATP, its protein structure, how it reacts to pests and how it may signal growth. The study, “Extracellular ATP signaling in plants,” was published in Science, and includes research from Sang Yeol Lee with the Plant Molecular Biology & Biotechnology Research Center, Gyeongsang National University in Korea. The study was funded in part by grants from the U.S. Department of Energy – Basic Energy Sciences and the Republic of Korea.

International Wheat Genome Sequencing Consortium to receive €1 million from Bayer CropScience for physical map completion
The International Wheat Genome Sequencing Consortium (IWGSC) announced it will receive approximately €1 million (EUR) over the next six months from Bayer CropScience (BCS) to support physical mapping of several wheat chromosomes. The goal of BCS’s contribution is to accelerate the consortium’s wheat genome sequencing effort by enabling the completion of physical maps for all 21 chromosomes. These maps are the foundation for obtaining ultimately a complete reference sequence of the hexaploid bread wheat genome, expected by 2016-17. The DNA sequence of the wheat genome will provide an essential tool for identifying and studying the function of wheat genes and support efficient breeding of new varieties.
 
The results of the BCS contribution will be made publicly available and will provide industry and academic scientists increased knowledge about the molecular basis of key traits in wheat. Concurrently, plant breeders and farmers around the world will gain essential resources to accelerate their breeding programs and develop more sustainable wheat varieties with increased tolerance to biotic and abiotic stresses.
 
Timing of nitrogen applications can enhance yields
Growers are doing a better job of managing nitrogen fertilizer applications. In recent years, the amount of fertilizer used has remained relatively constant while average yields have steadily increased. DuPont Pioneer experts suggest growers continue to look for ways to make the application of nutrients — particularly nitrogen — as efficient as possible. One strategy is to adopt split applications.

“Modern hybrids take up nitrogen later in the growing season,” says John Shanahan, DuPont Pioneer research scientist. “Data suggest applying nitrogen during the growing season, to coincide better with crop uptake of this nutrient, can result in higher yields.”

Growers know the pros and cons of fall nitrogen (N) application. While it may be necessary to apply fertilizer before winter, there are ways to minimize the potential for leaching and runoff. “Growers can mitigate losses from fall application by applying anhydrous ammonia after the soil temperature has dropped below 50 degrees — assuming it doesn’t warm up again for a lengthy period,” Shanahan says. “Also, N stabilizers can help keep nitrogen in the stable ammonium form.”

Some states even mandate withholding application until after a certain date and/or the use of a stabilizer.

Spring application of nitrogen leaves less time for leaching, but unpredictable weather can make it difficult for some growers to get into the field.

“Early planting trends can work against spring applications,” Shanahan says. “Many growers want to get seed in the ground as early as practical, and they don’t want to deal with fertilizer application if it may delay planting.”

Recent work by Tony Vyn at Purdue University demonstrates a substantial positive impact from applying nitrogen after planting. This is not surprising, as crops require the lion’s share of their nitrogen needs just before the reproductive stages.

“Growers must overcome some obstacles to make a second nitrogen application in season,” Shanahan says. “They need high-clearance equipment, which is expensive. They’re also at the mercy of weather: Can they get into the field in a timely manner to get the second application down?”

The industry is making strides to help growers find better ways of timing nitrogen applications. “It’s incumbent on our industry to help growers find practical solutions,” Shanahan asserts. “Crop sensors are one technology that adjusts side-dress N application rates for weather effects such as excessive rainfall.” The result can be increased yields, improved profits, and more efficient fertilizer use.

Because of the complex nature of soil and weather variability, growers face significant challenges in optimizing the amount of N to apply to each field, year and area within a field.  This results in under-application of N in some years and fields, with resulting yield losses and over application of N in other years and field areas resulting in inefficient use of N resources.

For example, through analysis of data compiled from hundreds of N rate response studies conducted throughout the Corn Belt over several years designed to determine economic optimum N rate, Pioneer has determined growers are potentially losing on average around $55/acre of revenue due to a combination of over- or under-application of N.

Pioneer is working to provide real-time information to help growers make better decisions on N applications, such as when and how to apply, what soils to apply and optimum application rates.  Also, Pioneer is working internally and with collaborators to understand the mechanisms of in-season nitrogen application. The information and the process developed should help growers make better decisions, reduce risk and increase crop yields.

“Generally, it pays to avoid putting all your nitrogen down at once.” Shanahan says. “Today’s genetics show potential to deliver more bang for your buck through split applications.”

Sources: University of Missouri, DuPont Pioneer, Iowa State University, International Wheat Genome Sequencing Consortium

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