About Us | Help Videos | Contact Us | Subscriptions
 

Managing wheat streak mosaic virus across the Great Plains

 

Researchers estimate between $60 to $400 in yield losses per acre occur in the Texas High Plains alone due to wheat streak mosaic virus or WSMV infection. But the losses go far beyond the borders of Texas. In the Great Plains, one of the largest wheat regions in the nation, and other parts of the world, WSMV is one of the most important biotic stresses affecting wheat (Triticum aestivum L.) productivity. The virus has been found in all major wheat-growing regions of the world.

            Cultural control is not very effective because the wind can spread the wheat curl mites, which vector the devastating disease, said Dr. Shuyu Liu, Texas A&M AgriLife Research small grains geneticist in Amarillo. And there is no effective chemical treatment available for the disease. The most cost-effective and environmentally safe approach for combating this disease is host resistance.

BREEDING FOR A CURE

            Breeding for wheat cultivars with resistance provides a socioeconomic and environmentally sustainable approach for combating WSMV. The use of markers as a proxy for quantitative and qualitative traits is widely applied in crop improvement programs. Among the available markers, single nucleotide polymorphisms (SNPs) are routinely used in plant breeding programs to distinguish potentially superior genotypes with genetic merit for traits of interest.

            The wheat genetics research team at Amarillo led by Liu outlined how the better control will come through genetics in three papers published in Crop Science  – “Wheat Curl Mite Resistance in Hard Winter Wheat in the U.S. Great Plains,” “Saturated Genetic Mapping of Wheat Streak Mosaic Virus Resistance Gene Wsm2 in Wheat” and “Development and Validation of KASP Markers for Wheat Streak Mosaic Virus Resistance Gene Wsm2.”

            Three closely linked kompetitive allele specific PCR (KASP) SNPs were identified as being effective in differentiating resistant and susceptible genotypes. Comparative mapping was performed using sequences of SNPs flanking Wsm2 and identified candidate genes and regions in Brachypodium and rice. The KASP SNPs developed in this study should be useful for marker-assisted selection of Wsm2 in wheat breeding programs, and the newly constructed map will also facilitate map-based cloning of Wsm2.

            In the second paper, Liu said they were able to locate the Wsm2 gene onto the chromosome 3BS with 90K SNPs and validate the gene in two populations derived from RonL and Snowmass and validate the KASP markers in six F2 breeding populations for marker-assisted selection for this gene. However, breeders have to be careful when they apply these markers as they will not work in some genetic backgrounds.

TAM SOLUTIONS

            TAM 112 is a popular cultivar for its drought tolerance and has been identified by the Texas A&M wheat breeding program as having resistance to wheat curl mite and wheat streak mosaic virus under field conditions.

            The researchers identified two Texas collections of wheat curl mite. All wheat lines with 1AL.1RS translocation are resistant to the collection 1 but susceptible to Texas collection 2. However, the resistance gene from Aegelops tauschii PI268210 that was transferred into TAM 112 and TAM 204 is resistant to the Texas collection 2, which exists in Kansas and Nebraska and is correlated to Australian type 1 of mite. This gene in a cultivar can provide very good protection when the mites are epidemic.

            Through the newly developed protocol, Liu’s team determined that TAM 112 and its derived lines, including TAM 204, Byrd and Avery, have the resistance gene from Aegilops tauschii, an annual goatgrass that is an ancestor of bread wheat.