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Rust resistance in exotic wheat germplasm tested through molecular genotyping and field trials across Himalayan region of Pakistan.

. Aamir Iqbal, Iqbal Munir, Syed Sartaj Alam and Sajid Ali


Abstract

Stem rust, caused by Puccinia graminis Pers. f. sp. tritici Eriks and E. Henn, poses an important risk for wheat production, worldwide. Though its infestation is low in Pakistan, screening of germplasm should be done for preparedness against the novel emergence as observed in for Ug99 (strain TTKS) and its variants. In this study, a set of 30 exotic wheat lines were screened in field (during 2018 to 2022) for stem rust disease in the Himalayan region of Pakistan. The field surveillance across these 38 environments (as location x years combinations) revealed that no stem rust was observed at any of the tested locations and therefore necessitated to use molecular markers to screen for stem rust resistance. Molecularly genotyping was done with eight DNA markers linked to resistance genes (Sr34, Sr31, Sr38, Sr57, Sr58, Sr39, Sr24, and Sr21). The molecular marker-based screening revealed that Sr57 gene linked marker was detected in 100% of the wheat lines followed by Sr34 and Sr58-linked marker which was detected in 97% of the tested wheat lines. 93% of the wheat lines showed the presence of Sr38 linked marker. The Sr31linked marker was detected in 30% of lines whereas 27% had Sr31 linked marker; 23% had Sr21; and 13% had Sr24 gene. The Exotic wheat line SA-Wht-14 showed the presence of the maximum seven Sr resistance genes (Sr34, Sr31, Sr38, Sr57, Sr58, Sr39, and Sr24). whereas the wheat line SA-Wht-4 showed the presence of the minimum three Sr resistance genes (Sr34, Sr38, and Sr57). The variability observed could be utilized for breeding resistant wheat varieties in the context of potential invasions in future.

Keywords: Wheat, stem rust, breeding, resistance, European

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