Fighting A Wheat Pathogen

Stem rust, caused by a number of varieties of the fungus Puccinia graminis, is a serious disease of wheat and barley. One variety of wheat stem rust, called Ug99, is particularly virulent, causing up to 100% crop losses. This pathogen affects most varieties of wheat that are grown today. Ug99 has spread throughout eastern Africa, and has also been detected in Yemen and Iran. While there are wheat lines that have been identified as resistant, these lines are not generally the high-yielding varieties that are useful for large-scale farming. The further spread of Ug99 could cause a disaster for food production.

Research Molecular Geneticist Nirmala Jayaveeramuthu and Adjunct Assistant Professor Matthew Rouse (Plant Pathology; USDA-ARS Cereal Disease Laboratory) study wheat-rust resistance genes in wheat and barley. Their lab uses MSI resources to map these genes. Should it be possible to identify molecular markers that are linked to resistance genes, plant breeders might be able to use them to develop strains of wheat resistant to Ug99.

In a project funded by the Bill and Melinda Gates Foundation and the US Department of Agriculture, the Rouse lab has been studying the wheat cultivar Gabo 56, which is resistant to Ug99. They have crossed this cultivar with Chinese spring wheat, a susceptible variety. Both Ugg99-susceptible and resistant progeny have resulted from this crossing. The group is now working with the RISS group to implement a novel method to analyze RNA-Seq data and identify cDNA sequences linked to the resistance gene. Using a de novo transcriptome assembly, transcripts with segregated expression are identified and SNPs are identified and used to create markers to finely map the resistance gene.

Image description: Left: Sample of genetic results of crossing susceptible and resistant plant. Right: Wheat “family tree” with genetic information.

posted on February 5, 2014

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