Barclay I

Jose K

Lagudah, E

Loughman R

Shankar M

Wilson R

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 1Wyalkatchem reselections differentiate the adult plant resistance gene Yr29 in an Australian wheat back-ground Loughman R1, Lagudah ES2, Shankar M1, Wilson R1, Jose K1 and Barclay I1 1 Department of Agriculture and Food, Western Australia and 2 CSIRO Plant Industry, Canberra  BACKGROUND Stripe rust, caused by Puccinia striiformis f.sp. tritici, is an important disease of wheat in Australia (McIntosh et. al. 1995).  The disease has been present in Australia since 1979 but was not detected in Western Australia until 2002 (Wellings et. al. 2003).  Consequently there had been comparatively little prior selection of Western Australian wheat breeding germplasm for resistance to stripe rust and limited knowledge of the extent and type of resistance present in locally adapted germplasm. The commercial variety Wyalkatchem (Machete/ Gutha..2*Jacup.11ISEPTON135) is the major wheat variety in Western Australia, estimated to represent 30% of wheat area sown in 2007/08.  Wyalkatchem possesses partial resistance and understanding its genetic control will assist breeding to improve stripe rust resistance and adaptation. WYALKATCHEM RESPONSE TO STRIPE RUST Under natural infection with pathotype 134 E16 A+ in the field, the wheat variety Wyalkatchem was observed to be mixed for response to stripe rust.  A low frequency of individual Wyalkatchem plants lack partial resistance and reach very high terminal rust severity.  The majority of individual Wyalkatchem plants express partial resistance.  Among 60 single plants re-selected at random and evaluated for adult plant resistance to stripe rust in the field at two sites in 2005, 2 were highly susceptible (80-100S) and were presumed to lack the partial resistance factor(s).   Remaining lines expressed partial resistance (30-70MS). ASSOCIATION OF PARTIAL RESISTANCE WITH Yr29 Yr29 has been mapped to chromosome 1B (William et. al. 2003, 2006). Preliminary mapping of stripe rust resistance in a Wyalkatchem derived doubled haploid population identified a stripe rust resistance QTL linked to Xwmc44 on chromosome 1BL, most likely Yr29 (M. Hayden pers. comm.). A sample of unselected Wyalkatchem, two highly susceptible single plant selections and 4 partially resistant single plant selections were tested with a novel single nucleotide polymorphism CAPS marker, csLV46.  The marker is located at the 1BL locus co-segregating with Lr46/Yr29/Pm39.  The marker assay clearly distinguished Wyalkatchem re-selections that differed in the stripe rust APR response (Table 1). Table 1. Terminal rust severity and csLV46 genotype of Wyalkatchem and 6 single plant selections of Wyalkatchem representing variants with and without adult plant resistance.    Figure 1. PCR products of csLV46 of Wyalkatchem and 6 single plant selections of Wyalkatchem representing variants with and without adult plant resistance, with reference to the control variety Atilla possessing Yr29. DISCUSSION The single plant reselected Wyalkatchem individuals provide potential ‘near-isogenic’ genetic stocks with and without Yr29.  These stocks are likely to be useful in developing improved understanding of the expression of partial resistance to stripe rust in an Australian wheat background, which can be influenced by environmental factors.  The use of Wyalkatchem as a donor of stripe  % Stripe Rust Severity csLV46  Manjimup (2 observers) South Perth*  genotype**  Obs. 1 Obs. 2   Wyalkatchem 30 70 - BWyalkatchem-003 30 50 0 B Wyalkatchem-016 30 60 0 B Wyalkatchem-018 100 100 80 A Wyalkatchem-045 30 60 0 B Wyalkatchem-048 30 60 0 B Wyalkatchem-049 100 100 80 A * as active sporulation **Yr29 absent (A) or present (B) Wyalkatchem Wyalkatchem-003 Wyalkatchem-016 Wyalkatchem-018 Wyalkatchem-045 Wyalkatchem-048 Wyalkatchem-049 Atilla (Yr29 check)  2 rust resistance is enhanced by the knowledge that it possesses Yr29, though care should be taken in breeding to avoid a small proportion of individual plants lacking this resistance.  Enhancing stripe rust resistance through breeding for resistance gene combinations should be improved with this knowledge. ACKNOWLEDGEMENTS Preliminary mapping of Yr29 in Wyalkatchem was undertaken through the Australian Winter Cereal Molecular Marker Program, supported by the Grains Research and Development Corporation. REFERENCES McIntosh R.A., Wellings C.R., Park R.F. (1995) Wheat Rusts, An Atlas of Resistance Genes.  CSIRO Australia. Wellings C.R., Wright D.G., Keiper F., Loughman, R. (2003) First detection of wheat stripe rust in Western Australia: evidence for a foreign incursion.  Australasian Plant Pathology. 32:321-322. William M., Singh R.P., Huerta-Espino J., Ortiz Islas S., Hoisington, D. (2003) Molecular marker mapping of leaf rust resistance gene Lr46 and its association with stripe rust resistance gene Yr29 in wheat. Phytopathology 93:153-159. William H.M., Singh R.P.;  Huerta-Espino J.,  Palacios G.,  Suenaga K. (2006) Characterization of genetic loci conferring adult plant resistance to leaf rust and stripe rust in spring wheat. Genome  49: 977-990. 

Wyalkatchem reselections differentiate the adult plant resistance gene Yr29 in an Australian wheat background

https://ses.library.usyd.edu.au/bitstream/2123/3459/1/P133.pdf

Wyalkatchem reselections differentiate the adult plant resistance gene Yr29 in an Australian wheat background

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