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Research Project: Genetic Improvement of Small Grains for Biotic and Abiotic Stress Tolerance and Characterization of Pathogen Populations

Location: Plant Science Research

Title: Identification of PmTA1662 from Aegilops tauschii

Author
item WIERSMA, ANDREW - Michigan State University
item PULMAN, JANE - Michigan State University
item BROWN, LINDA - Michigan State University
item Cowger, Christina
item OLSON, ERIC - Michigan State University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2017
Publication Date: 3/3/2017
Citation: Wiersma, A., Pulman, J., Brown, L., Cowger, C., Olson, E. 2017. Identification of PmTA1662 from Aegilops tauschii. Theoretical and Applied Genetics. 130:1123-1133.

Interpretive Summary: Powdery mildew is a threat to wheat production worldwide, and the rapid breakdown of race-specific resistance to Blumeria graminis (DC.) f. sp. tritici (Bgt) reinforces the need to identify novel sources of resistance. One of the ancestors of common wheat, Aegilops tauschii, is an excellent source of disease resistance that can be transferred into modern wheat. A population segregating for powdery mildew resistance was developed by crossing the resistant Ae. tauschii accession TA1662directly with the susceptible hard white wheat line KS05HW14. After backcrossing to KS05HW14, a population of 96 introgression lines (ILs) was developed. A laboratory assay was used to screen the ILs and resistance was found to behave as a single locus. The resistance gene, referred to as PmTA1662, mapped to wheat chromosome 2DS. PmTA1662 was evaluated in replicated field trials in two years, and a single DNA segment was identified that reduced powdery mildew severity and explained 21% of field variation (P-value < 0.01). Four molecular markers linked to PmTA1662 were identified. This novel source of powdery mildew resistance and closely linked genetic markers will support ongoing efforts to develop wheat varieties with powdery mildew resistance.

Technical Abstract: Powdery mildew remains a significant threat to wheat (Triticum aestivum L.) production, and the rapid breakdown of race-specific resistance to Blumeria graminis (DC.) f. sp. tritici (Bgt) reinforces the need to identify novel sources of resistance. The D-genome progenitor species of hexaploid wheat, Aegilops tauschii is an excellent source of disease resistance that is transferrable to T. aestivum. A population segregating for powdery mildew resistance was developed by crossing the resistant Ae. tauschii accession TA1662 (2n = 2x = DD) directly with the susceptible hard white wheat line KS05HW14 (2n = 6x = AABBDD). Normal chromosome segregation was restored by backcrossing to KS05HW14, and a population of 96 BC2F4 introgression lines (ILs) were developed. Genotyping-by-sequencing was used to generate genome-wide genetic maps that were anchored to the Ae.tauschii reference genome. Approximately 48% of the D-genome genetic space was segregating for Ae. tauschii alleles. A detached-leaf Bgt assay was used to screen BC2F4:6 ILs and resistance was found to segregate as a single locus (' = 2.0, P-value = 0.157). The resistance gene, referred to as PmTA1662, mapped to wheat chromosome 2DS. PmTA1662 was evaluated under field conditions in replicated trials in 2015 and 2016. In both years, a single QTL spanning the PmTA1662 locus was identified that reduced powdery mildew severity and explained 21% of field variation (P-value < 0.01). KASPTM assays were developed from closely linked GBS-SNP markers, a refined genetic map was developed, and four markers that cosegregate with PmTA1662 were identified. This novel source of powdery mildew resistance and closely linked genetic markers will support ongoing efforts to develop wheat varieties with powdery mildew resistance.