Disease resistance is critical in soft red winter wheat (Triticum aestivum L.) cultivars. Leaf rust caused by Puccinia triticina Eriks and stripe rust caused by Puccinia striiformis Westend. f.sp. tritici Eriks. are destructive pathogens of wheat. From 2014 to 2015 phenotypic data was collected at diverse locations for resistance to leaf rust (North Carolina, Texas, and Virginia) and stripe rust (Arkansas, North Carolina, Georgia, Texas, and Virginia) in a Pioneer ‘25R47’ /‘Jamestown’ (P47/JT) population composed of 186 F5:9 recombinant inbred lines (RILs). Analysis of the P47/JT population identified two quantitative trait loci (QTL) for leaf rust resistance on chromosome 5B and two QTL for stripe rust resistance on chromosomes 3B and 6A. Phenotypic variation (%) explained by the putative leaf rust resistance QTL of Jamestown on 5B was as high as 22.1%. Variation explained by the putative stripe rust resistance QTL of Jamestown on 3B and 6A was as high as 11.1 and 14.3%, respectively.
Jamestown is postulated to contain gene Lr18. Seedlings of 186 F5:9 recombinant inbred lines from the P47/JT population and 200 F2 seedlings from eight other crosses including Jamestown and/or the Lr18 host differential line RL6009 (Thatcher*6/Africa 43) were screened with P. triticina race TNRJJ. Genetic analysis of the populations was conducted to validate the presence of Lr18 in Jamestown. Results of linkage analysis identified SNP maker IWB41960 linked within 5 cM of gene Lr18 in all three populations.
From 2016 to 2017 phenotypic data was collected at diverse locations for resistance to leaf rust (Illinois, North Carolina, and Virginia) in a ‘2013412’ (PI 667644) / VA10W-21 (PI 676295) population (412/21) composed of 157 doubled haploid (DH) lines. The 412/21 DH lines were genotyped via genotyping by sequence (GBS). Analysis of the 412/21 population identified one quantitative trait loci (QTL) region associated with adult plant resistance to leaf rust on chromosome 1B. Phenotypic variation (%) explained by the putative leaf rust resistance QTL of 2013412 on 1B was as high as 40.1%. Kompetitive allele-specific (KASP) markers KASP_S1B_8414614 and KASP_S1B_8566239 were developed as markers for use in marker assisted selection. / Ph. D. / Disease resistance to leaf rust and stripe rust is important when growing soft red winter wheat. Genetic resistance can have a benefit to cost ratio of up to 27:1, considerably better than that of fungicide treatments. From 2013 to 2017 disease data was collected across multiple locations spanning the eastern United States (Arkansas, Georgia, Illinois, North Carolina, Texas, and Virginia). DNA molecular markers were used to identify specific chromosome regions containing genes associated with leaf and stripe rust resistance. DNA markers associated with genes conferring resistance to leaf rust resistance were identified in three chromosome regions, and genes in two regions were associated with stripe rust resistance. These genes and molecular markers associated with them can be used by scientists to further enhance resistance in wheat cultivars.
Another study was conducted to determine if Lr18, a gene for leaf rust resistance that has a large effect, is present in the Virginia Tech soft red winter wheat breeding material. This gene (Lr18) is known to have been introduced from an ancestral species highly related to wheat. Wheat seedlings derived from crosses between lines postulated to carry Lr18 with susceptible lines were tested for resistance to a specific strain of leaf rust lacking virulence to Lr18. Genetic analysis of the ratio of resistant versus susceptible seedlings and association between DNA molecular markers and resistant seedlings were conducted to validate the presence of gene Lr18. A molecular marker linked tightly to gene Lr18 was identified in the study. This gene was found to be widely distributed in soft red winter wheat breeding materials and the molecular marker associated with gene Lr18 will be useful for scientists to further improve resistance in wheat cultivars.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/89628 |
| Date | 04 December 2017 |
| Creators | Carpenter, Neal Ryan |
| Contributors | Crop and Soil Environmental Sciences, Griffey, Carl A., Baudoin, Antonius B., Saghai-Maroof, Mohammad A., Holliday, Jason A. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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