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NEW SOURCES OF WHEAT YELLOW RUST (PUCCINIA STRIIFORMIS F. TRITICI) SEEDLING RESISTANCE

SUMAIRA RIZWAN¹, IFTIKHAR AHMAD², MOHAMMAD ASHRAF¹, GHULAM MUSTAFA SAHI², JAVED IQBAL MIRZA², ATIQ-UR-REHMAN RATTO² AND ABDUL MUJEEB-KAZI³

Abstract: Wild relatives of wheat as new sources of genetic diversity are a potent resource for addressing biotic and abiotic stress constraints that limit wheat productivity. These are distributed in the three gene pools of the Triticeae and over the last two decades are being extensively utilized in breeding programmes globally. In this study, 200 accessions of Triticum turgidum (2n=4x=28; AABB), 40 accessions of Aegilops tauschii (2n=2x=14;DD), and 6 accessions of Ae. triuncialis (2n=4x=28;CCUU) were screened against stripe rust of wheat (Puccinia striiformis tritici) at seedling stage. Bulk inoculum collected from environmentally diverse wheat growing areas of Pakistan was used for the seedling screening. The innoculum had virulence for genes Yr1, Yr3, Yr4, Yr5, Yr6, Yr7, Yr8, Yr9, Yr18, YrSp, YrSD, and YrCV. Infection types (ITs) ranging from low to high were recorded within each germplasm category where 35 durum lines (T. turgidum,) and 13 of Ae.tauschii had good seedling resistance (0-2). Another 20 durum and 12  Ae. tauschii lines were found moderately resistant. Frequency distributions of the ITs was higher for Ae. tauschii lines (34%) as compared to the durum wheats (20%). Advanced germplasm testing involving synthetic hexaploid wheats have made available several lines that are resistant to stripe rust. The source of resistance in this germplasm is attributed to alleles on the A and B genomes of durum parents, or on the Ae. tauschii’s D genome, or is a combination of genes that are pyramided as a consequence of A, B and D genome hybridizations. Ample diversity has been identified that warrants exploitation in wheat breeding.

¹Quaid-e-Azam University, Islamabad, Pakistan.

²National Agricultural Research Center (NARC), Islamabad, Pakistan

³National Institute of Biotechnology & Genetic Engineering (NIBGE), Faisalabad, Pakistan