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Making Wheat Better Equipped to Fight Fungal Disease

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Agricultural Research Service (ARS) scientists and their partners published a study today that should boost efforts to develop new varieties of wheat that are better equipped to resist a fungal disease that threatens global wheat production each year.

The report in Nature Genetics, by Guihua Bai and his colleagues identifies a key gene that could be used as an important genetic resource by wheat breeders worldwide to address the constant challenge posed by Fusarium head blight (FHB). FHB, also known as "scab," thrives in warm and moist conditions and is becoming an increasing threat worldwide because of the unpredictable weather patterns brought on by climate change and an increasing trend toward more corn production and no-till farming, which both increase the availability of the pathogen in fields. The disease has caused an estimated $2.7 billion in losses, in Minnesota alone since the 1990s, and forced many wheat and barley farmers there into bankruptcy. Growers often use fungicides to control it.

Bai, a plant molecular geneticist with the ARS Central Small Grain Genotyping Laboratory, in Manhattan, Kansas, and his colleagues showed that a gene, known as TaHRC, plays a key role in conferring resistance to FHB. The findings may be applied to breeding improved varieties of wheat, the researchers say.

The best FHB resistance in today's wheat varieties and germplasm is largely based on a suite of genes discovered years ago in a Chinese wheat variety known as Sumai 3 and its derivatives. But pinpointing the specific genes that are the sources of resistance within genomic regions—which would help breeders move them into locally adapted wheats to develop new varieties—has proved to be challenging. Screening experimental plants for disease resistance traits requires inoculating thousands of plants in disease screening nurseries and evaluating results that are often inconsistent. This screening process must be repeated over several growing seasons and often multiple locations to ensure that a desirable gene, or trait, is passed down to subsequent generations.

The discovery is the result of more than 10 years of research by an international team that used both modern genomic tools and traditional genetic techniques. In their study, the researchers managed to confirm the role played by the TaHRC gene by essentially "switching it off," which modified production of key proteins and significantly increased FHB resistance. Inactivating the gene in such a way does not produce wheat that is genetically modified or with an increased risk of triggering gluten allergies, the researchers say.

Since the natural variant of TaHRC is available in Sumai 3 and its derivatives, it can be transferred into new wheat varieties through traditional breeding. Bai's lab also developed DNA tags that can be used to quickly and accurately select breeding lines without having to screen thousands of wheat lines in large nurseries.

Along with Bai, study authors include Paul St. Amand, a plant geneticist with the ARS Hard Winter Wheat Genetics Research Unit in Manhattan, and a team from Kansas State University that included Zhenqi Su, Amy Bernardo, Bin Tian, Hui Chen and Harold Trick.

Reference: Su et al. 2019. A deletion mutation in TaHRC confers Fhb1 resistance to Fusarium head blight in wheat. Nature Genetics. DOI:https://doi.org/10.1038/s41588-019-0425-8.

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