Assessment of Genetic Diversity for Stem Rust and Stripe Rust Resistance in an International Wheat Nursery Using Phenotypic and Molecular Technologies

Abstract

The objective of this study was to assess diversity for stem rust and stripe rust resistance
in an international wheat screening nursery under greenhouse conditions using pathotypes with
known avirulence/ virulence profiles. A set of 95 entries of an international wheat screening nursery
collected from material generated by staff of the International Maize and Wheat Improvement Centre
(CIMMYT) was tested against seven Australian Pgt and five Pst pathotypes through artificial
inoculation under the greenhouse conditions using standard procedures. Ten all-stage stem rust
resistance genes (Sr8a, Sr8b, Sr9b, Sr12, Sr17, Sr23, Sr24, Sr30, Sr31 and Sr38) and seven all-stage
stripe rust resistance genes (Yr3, Yr4, Yr6, Yr9, Yr17, Yr27 and Yr34) were postulated either singly
or in combinations based on seedling responses of test entries against pathotypes differing in
virulence for commonly deployed genes. Sr30 and Sr38 were the most common stem rust resistance
genes in this nursery. The Sr38-linked stripe rust resistance gene Yr17 was present in high proportion.
The presence of rust resistance genes Sr24, Sr31/Yr9, Sr38/Yr17 and Yr4 were confirmed using the
closely linked molecular markers. The adult plant resistance (APR) genes Sr2 and Lr34/Yr18/Sr57
were detected using linked molecular markers csSr2 and csLV34, respectively. Genotypes carrying
combinations of stem rust and stripe rust resistance were identified for use as donor sources in
breeding programs.