Jinxiu Zhang

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Plant Science


The development of stem rust resistant wheat has played a significant role in the control of this disease. A number of stem rust resistance genes (Sr genes) confer resistance to a wide range of races of the stem rust pathogen (Puccinia graminis f. sp. tritici). Sr26 is an important stem rust resistance gene and its presence, in combination with other resistance genes, confers a high level of resistance. This gene was introgressed into wheat from Elytrigia elongata. In order to determine the presence of Sr26 in a complex genetic background of other stem rust resistance genes, a genetic marker for Sr26 gene is needed. In this study, we attempted to tag Sr26 using the random amplified polymorphic DNAs (RAPDs) technique. A segregation population for Sr26 was developed using a cross between LMPG-6 (a stem rust susceptible line) and Sr26/9*LMPG (a near-isogenic line of LMPG-6 with Sr26). F2 and F2,3 plants were evaluated to detennine the genotypes for stem rust reactions. Genomic DNAs were isolated from LMPG-6, Sr26/9*LMPG and 95 F2:3 resistant and susceptible plants. Polymorphisms between the near-isogenic lines, Sr26/9*LMPG and LMPG-6, were evaluated with 300 random primers. Nine primers did not produce amplification products, and others amplified averaged about 5 fragments each. Seven out of 300 primers produced polymorphic bands between the two parents. These primers were tested against the DNA bulks of F2,3 resistant and susceptible plants. The polymorphic fragment (OPH-11850) generated by OPH-11 (a 5'-CTTCCGCAGT-3' decamer) was present in Sr26/9*LMPG, F2:3 resistant DNA bulks and most of the families with Sr26 gene. OPH-11850 was absent in LMPG-6, F2,3 susceptible bulks and most of families without Sr26. The OPH-l 1850 marker was found to be closely linked (5.6 mapping units) to the stem rust resistance gene, Sr26. Other primers that generated polymorphic bands between the parents failed to produce the same polymorphisms in repeated experiments. The Marker OPH-11850 was cloned into pGEM-T Easy and used in Southern hybridizations to test relationship with resistance. OPH-11850 showed a distinct hybridization band with the resistance F2:3 individual families that had it in RAPD experiments and did not hybridized with DNA from susceptible F2,3 families without it in RAPD experiments. The OPH-11850 marker can be used as a marker for identification of the stem rust resistance gene 26.

Library of Congress Subject Headings

Wheat -- Disease and pest resistance -- Genetic aspects Puccinia graminis Wheat rusts



Number of Pages



South Dakota State University