|Liu, Jean - PIONEER HI-BRED INTNATL|
Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 9, 2002
Publication Date: September 1, 2002
Citation: KOLMER, J.A., LIU, J.Q. INHERITANCE OF LEAF RUST RESISTANCE IN THE WHEAT CULTIVARS AC MAJESTIC, AC SPLENDOR, AND AC KARMA. CANADIAN JOURNAL OF PLANT PATHOLOGY. 2002. v. 24. p. 327-331. Interpretive Summary: Three recent wheat cultivars from western Canada were examined to determine the number and identity of genes for resistance in the cultivars to the disease leaf rust of wheat. The three cultivars, AC Majestic, AC Splendor, and AC Karma, were all found to have leaf rust resistance genes Lr13 and Lr16. AC Splendor also had gene Lr34, and AC Karma had gene LrTb. Genes Lr13 and Lr16 are also present in many other U.S. and Canadian wheats, yet wheat cultivars with these genes currently do not have very good levels of leaf rust resistance. Cultivars with genes Lr34 and LrTb have only moderate levels of leaf rust resistance, as other genes are needed to provide high levels of resistance in addition to these genes. The results of this study indicated a lack of genetic diversity for leaf rust resistance genes in recent Canadian spring wheats. Other resistance genes that currently provide good resistance to leaf rust must be added to wheat breeding programs in Canada and the U.S. in order to develop leaf rust resistant wheat cultivars. These research results can be used to help wheat breeders develop wheat lines with improved resistance to leaf rust.
Technical Abstract: The wheat cultivars AC Majestic, AC Splendor, and AC Karma, were developed and licensed for production in western Canada in the mid 1990s. Leaf rust caused by Puccinia triticina, is an important pathogen of wheat throughout North America. Virulent isolates of P. triticina are selected following the release of wheats with specific resistance genes, which eventually reduces the effectiveness of the resistance. Knowledge of the genes that condition leaf rust resistance in wheat makes it easier to add additional resistance genes to wheat breeding germplasm. The objective of this study was to identify the leaf rust resistance genes in these three cultivars. The three cultivars were crossed with the susceptible wheat Thatcher, and the F1 plants were backcrossed to Thatcher. The backcross F2 (BCF2) families were tested for segregation of leaf rust resistance in seedling tests with specific P. triticina isolates. The BCF2 families were also tested for segregation of leaf rust resistance as adult plants in a field rust nursery that had been inoculated with a mixture of P. triticina virulence phenotypes. AC Majestic was determined to have the seedling resistance gene Lr16, and the adult plant resistance gene Lr13. AC Splendor was determined to have Lr13, Lr16, and the adult plant resistance gene Lr34. AC Karma was determined to have Lr13, Lr16, and the adult plant resistance gene LrTb. All three cultivars had genes Lr13 and Lr16, which reflects a lack of genetic diversity for leaf rust resistance in western Canada spring wheats. The results of the study indicate that additional leaf rust resistance genes need to be crossed into the spring wheat germplasm to provide cultivars that maintain high levels of leaf rust resistance.