Determination of heterozygosity for avirulence/virulence loci through sexual hybridization of Puccinia striiformis f. sp. tritici

Abstract

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is one of the most devastating diseases of wheat worldwide and resistant cultivars are vital for its management. Therefore, investigating the heterozygosity of the pathogen is important because of rapid virulence changes in isolates heterozygous for avirulence/virulence. An isolate of P. striiformis f. sp. tritici was selfed on Berberis shensiana to determine the heterozygosity for avirulence/virulence loci. One hundred and twenty progeny isolates obtained from this selfing were phenotyped using 25 lines of wheat containing Yr genes and genotyped with 96 simple sequencing repeat markers, with 51 pathotypes and 55 multi-locus genotypes being identified. All of these were avirulent on lines with Yr5, Yr10, Yr15, Yr24 and Yr26 and virulent on lines with Yr17, Yr25 and YrA, indicating that the parental isolate was homozygously avirulent or homozygously virulent for these loci. Segregation was found for wheat lines with Yr1, Yr2, Yr4, Yr6, Yr7, Yr8, Yr9, Yr27, Yr28, Yr32, Yr43, Yr44, YrExp2, YrSp, YrTr1, YrTye and YrV23. The 17 cultivars to which the Pst was identified as heterozygous with respect to virulence/avirulence should not be given priority in breeding programs to obtain new resistant cultivars.

Keywords

• Puccinia striiformis f. sp. tritici|selfing|heterozygosity|virulence inheritance