Abstract
Growing resistant wheat varieties is a key method of minimizing the extent of yield losses caused by the globally important wheat leaf rust (LR) and stripe rust (YR) diseases. In this study, a population of 186 F8 recombinant inbred lines (RILs) derived from a cross between a synthetic wheat derivative (PI610750) and an adapted common wheat line (cv. “UC1110”) were phenotyped for LR and YR response at both seedling and adult plant stages over multiple seasons. Using a genetic linkage map consisting of single sequence repeats and diversity arrays technology markers, in combination with inclusive composite interval mapping analysis, we detected a new LR adult plant resistance (APR) locus, QLr.cim-2DS, contributed by UC1110. One co-located resistance locus to both rusts, QLr.cim-3DC/QYr.cim-3DC, and the known seedling resistance gene Lr26 were also mapped. QLr.cim-2DS and QLr.cim-3DC showed a marginally significant interaction for LR resistance in the adult plant stage. In addition, two previously reported YR APR loci, QYr.ucw-3BS and Yr48, were found to exhibit stable performances in rust environments in both Mexico and the United States and showed a highly significant interaction in the field. Yr48 was also observed to confer intermediate seedling resistance against Mexican YR races, thus suggesting it should be re-classified as an all-stage resistance gene. We also identified 5 and 2 RILs that possessed all detected YR and LR resistance loci, respectively. With the closely linked molecular markers reported here, these RILs could be used as donors for multiple resistance loci to both rusts in wheat breeding programs.
Highlights
Wheat leaf rust (LR) and stripe rust (YR), caused by the air-borne fungi Puccinia triticina (Pt) and Puccinia striiformis f. sp. tritici (Pst), respectively, are considered the primary biotic threats to wheat production globally (Todorovska et al, 2009)
A set of 48 differential lines with known LR resistance genes were included in the seedling tests to compare the infection types (ITs) of the parents and recombinant inbred lines (RILs) to those associated with known resistance genes
LR ITs were recorded 11 days post-inoculation based on the following scale modified from Roelfs et al (1992): “0” = no visible symptoms; “;” = only necrotic/chlorotic flecks without any uredinia; “1” = small uredinia surrounded by necrosis; “2” = small to medium uredinia surrounded by chlorosis or necrosis; “3” = medium-sized uredinia without chlorosis or necrosis; “4” = large-sized uredinia without chlorosis or necrosis; “X” = random distribution of variable-sized uredinia; “3C3” = medium-sized uredinia with chlorosis; “;11+” = necrotic/chlorotic flecks with small to medium uredinia; and “+” and “−” were used when uredinia were somewhat larger or smaller than normal for the ITs
Summary
Wheat leaf rust (LR) and stripe rust (YR), caused by the air-borne fungi Puccinia triticina (Pt) and Puccinia striiformis f. sp. tritici (Pst), respectively, are considered the primary biotic threats to wheat production globally (Todorovska et al, 2009). Using a population of 186 recombinant inbred lines (RILs) derived from a cross between these parents, four YR resistance QTL (two from UC1110 and two from PI610750) were identified and characterized under the CA rust environment The objectives of this follow-up study were to: (1) investigate the performance of these previously reported YR resistance loci in the Mexican rust environment; (2) identify potential sources of both seedling resistance and race non-specific APR to both LR and YR in this mapping population; and (3) Determine interactions between the identified resistance loci in the adult plant stage
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