Genetic Analysis of Stripe Rust Resistance in a Common Wheat Landrace Aus28166.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the major threats to global wheat production. Aus28166 is a wheat landrace collected from Iran in the 1920s and it has displayed resistance to current Australian Pst pathotypes both under the greenhouse and field conditions. Aus28166 was crossed with a stripe rust susceptible genotype Avocet S (AvS) and a recombinant inbred line (RIL) F₆ population was generated. Seedling tests on 104 F₆ Aus28166/AvS RILs in the greenhouse using Pst pathotype 134E16A+Yr17+Yr27+ showed the presence of two independent all stage resistance (ASR) genes (82 resistant: 22 susceptible, χ²_3:1 = 0.82, non-significant  at P=0.05 and 1 df) in Aus28166. The two different stripe rust ASR genes were named as ‘A’ and ‘B’ based on their typical seedling infection types (ITs) 11⁺c and 23c, respectively. In order to identify the genomic locations of these genes, DNA samples from 10 lines each with IT11+C, IT23c and IT3⁺ were bulked and bulked segregant analysis (BSA) was performed using the iSelect 90K Infinium assay. The BSA tentatively located stripe rust resistance genes ‘A’ and ‘B’ in chromosomes 5B and 3B, respectively. Two different single gene segregating populations from the Aus28166/AvS singly heterozygous F₃ families with different phenotypes are being advanced to F₆ generation to facilitate detailed mapping of these genes. Aus28166 has been crossed with two Australian cultivars to transfer the resistance genes to modern wheat backgrounds. Backcross-derivatives will also be useful for validation of linked markers.