Molecular and Virulence Characterisation of <i>Puccinia striiformis</i> Populations on Cereal Crops in Kazakhstan

ABSTRACT The deployment of Yr genes has long been a key strategy in wheat breeding programmes aimed at managing stripe rust caused by Puccinia striiformis . Emergence of new lineages originating from different plant hosts challenges the effectiveness of resistance. The resistance spectra of Yr genes across P. striiformis lineages from various hosts have not previously been explored in Kazakhstan. To address this gap, we genotyped P. striiformis isolates collected from wheat, triticale, barley and durum wheat using the Genobait (GBTS) 20K SNP array. Pathotyping of the isolates was performed using the Yr single‐gene set and the Chinese set of wheat lines. Genotyping revealed high genetic diversity in the P. striiformis populations from wheat (Simpson λ = 0.97), followed by barley (λ = 0.95) and triticale (λ = 0.92), while the lowest diversity was observed in the population from durum wheat (λ = 0.91). High gene flow and low F ST values among the isolates from the different cereal crops except barley suggested high genetic similarity. Genetic group G1 exhibited broad host adaptability, occurring on all four hosts, whereas G2 was mainly restricted to barley with limited overlap with triticale. Although predominant on barley, some G2 isolates also showed virulence to several Yr genes ( Yr1 , Yr6–9 , Yr17 , Yr43 , Yr44 , YrSp and YrExp2 ). The P. striiformis population in this region lacked virulence against Yr5 , Yr10 and Yr15 . These findings improve our understanding of the potential risks posed by different host‐associated lineages in reshaping the genetic structure of the stripe rust pathogen in Kazakhstan.

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