Genetic Analysis And Mapping Of Stirpe Rust Resistance In Aegilops Tauschii

Wheat stripe rust caused by fungus Puccinia striiformis Westend. f. sp. tritici (Pst), isone of the most devastating diseases in cereals all over the word. Stripe rust is also a regularthreat to wheat production in China. Resistant breeding is the most economical, safe andeffective way to control stripe rust in wheat, and genes resistant to stripe rust play afundenmental role in wheat resistant breeding. Many wild relatives of wheat contain novelresistance to wheat stripe rust. Identification and cloning of rust resistance genes in wildgermplasm will certainly enrich accessible gene pool for wheat improvement.Aegilops tauschii, the D genome progenitor of common wheat (Triticum aestivum), is animportant resource for wheat improvement. Ae.tauschii is classified into two subspecies: ssp.tauschii and ssp. strangulata. In this study, we characterized stripe rust responses in acollection of118Ae.tauschii accessions, analyzed inheritance of stripe rust resistance usingAe.tauschii F2populations and a mixture of Chinese Pst races, mapped the YrAS2388geneusing the iSelect10k SNP chip of Ae.tauschii, and evaluated stripe rust responeses of ansynthetic hexaploid wheat which carries the YrAS2388gene. Main results are addressedbelow.1. Among118Ae.tauschii accessions, all34ssp. strangulata accessions were resistant(IT1–3); of the84ssp. tauschii accessions,13were resistant and71were susceptible (IT7–9). All accessions resistant to stripe rust were originated from countries near the CaspianSea. Therefore, areas near the Caspian Sea are hotspots for evolution of stripe rust resistancein Ae.tauschii. Chi-square test further confirms the dependence between the Caspian Sea areaand stripe rust resistance in the current Ae.tauschii germplasm (P <0.01).2. We utilized60F2populations to investigate the nature of stripe rust resistance at the adultplant stage in Ae.tauschii. Thirty F2populations segregated for stripe rust response,29werehomogenous resistant, and one control population derived from a cross between susceptibleparents was homogenous susceptible. The30segregating populations were derived from18resistant accessions paired with susceptible parents. Resistance in10crosses involvingresistant ssp. strangulata accessions was in each case likely conferred by a single dominant orsemi-dominant gene, while resistance was recessive in other crosses. We inoculated29F2populations involving intercrosses of14resistant accessions and a cross between susceptibleparents, indicated the common presence of YrAS2388, previously mapped on chromosomearm4DS, in all resistant accessions.3. We then focused on two F2populations, derived from CIae9/PI560536andPI511383/PI486274, in which CIae9and PI511383were YrAS2388carrier. Ten susceptible F2individuals and both parents in each population were genotyped by the10k iSelect SNP chip of Ae.tauschii and the YrAS2388trait was mapped using bulked segregant analysis. EighteenSNP markers showed close linkage to stripe rust resistance, and the YrAS2388gene wasmapped to a11.8cM region on chromosome4DS.4. A synthetic hexaploid wheat line was developed from T. turgidum cv.‘Langdon’ andAe.tauschii CIae9. The synthetic hexaploid was more resistant (IT2–4) than its durum parent(IT6–8) at the adult plant stage. The resistant gene from CIae9probably conferred partialresistance at the hexaploid level.