Gene-based analysis of <Emphasis Type="Italic">Puccinia</Emphasis> species and development of PCR-based marker to detect <Emphasis Type="Italic">Puccinia striiformis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis> causing yellow rust of wheat

Stripe rust is considered as the current major rust disease affecting winter cereal production across the world. A quick, reliable PCR-based marker was developed here to detect, identify and rapidly monitor Puccinia striiformis f. sp. tritici (Pst) in wheat-growing areas. Three respective sets of primers, designed from β-tubulin, squalene monooxygenase and ketopantoate reductase genes selected from the full genome of Puccinia striiformis f. sp. tritici, amplified sequences of 239, 358 and 1518 bp, respectively, in Pst pathotypes. A fragment of 1518 bp unique to Pst pathotypes was amplified using primer set PstKeto F1_30/Pst KetoR1_1547 and distinguished the pathogen clearly from different Puccinia spp. and other fungal pathogens. The detection limit of the marker (KetoPstRA₁₅₀₀, accession no. KU240073) by conventional PCR assay was 10 pg. This marker could detect the pathogen in the host before symptom expression. The sensitivity and utility of the marker were further enhanced in a qPCR-based assay that was developed with a newly designed primer set PstKeto F1_1246/Pst KetoR1_1547, which amplified a product of 302 bp and detected as little as 10 fg of DNA. This PCR/qPCR based marker is suitable for studying cultivar resistance, which requires accurate quantification of the pathogen in diseased host tissue.