Production And Identification Of Wheat-Tetraploid Thinopyrum Elongatum 1BS·1EL Translocation Line With Stripe Rust-Resistance

Stripe rust is a devastating fungal disease of wheat caused by Puccinia striiformis f.sp.tritici（Pst）,which can significantly affect wheat yield and result in 5%to 60%yield reductions in wheat.Although the application of fungicide can control stripe rust,planting resistant varieties is an economic and environmentally friendly alternative.Therefore,to ensure the sustainable management of wheat stripe rust in China,there is a substantial need to discover new stripe rust resistance genes,identify resistance-associated molecular markers,and breed new disease-resistant wheat varieties.Thinopyrum elongatum is a perennial cold-season forage grass in Triticeae with three different ploidy levels,diploid,tetraploid,and decaploid.Abundant tillers,resistance to cold,drought and multiple wheat diseases make Th.elongatum a valuable genetic resource for wheat improvement.The wheat-tetraploid Th.elongatum 1E/1D substitution line K17-841-1（2n=6x=42,AABBEE）was developed by our research group.In this study,K17-841-1 was performed hybrid as a stripe rust resistance donor and crossed with the common wheat ph1b mutant（CSph1b）,afterwards,the F₁ was backcrossed to the CSph1b to obtain BC₁F₂.A new homozygous chromosome wheat-tetraploid Th.elongatum translocation line was obtained and verified as 1BS·1EL translocation line.The results are as follows:1.The genome in situ hybridization（GISH）analysis showed that K2021-120-20 contained42 chromosomes,in which a partial chromosome pair showed E genome signal.The fluorescence in situ hybridization（FISH）and FISH painting results revealed that the alien E genome in K2021-120-20 was the long arm of the 1E chromosome（1EL）translocated to the1B chromosome.The 55K SNP array analysis verified the cytogenetic result.We randomly selected 30 inbred offspring from K2021-120-20 to identified the cytogenetic stability using GISH.The results showed that 28 individual plants had the same chromosome composition as K2021-120-20.Therefore,K2021-120-20 is a cytogenetic stable wheat-tetraploid Th.elongatum homozygous 1BS·1EL translocation line.2.The results of strip rust resistance identification at seedling and adult stages showed that common wheat parents CSph1b,Chuanmai 42,Shumai 482,and Shumai 921 were susceptible to stripe rust,nevertheless,the 8801,1E/1D substitution lines K17-841-1,and K2021-120-20were highly resistance to stripe rust.Thus,we speculated that the strip rust resistance gene located at the long arm of 1E chromosome in the K2021-120-20.3.In total,2713 unique SSR sequences were specific to the 1E chromosome of diploid Th.elongatum.We randomly selected SSR of primers which distributed on the 1E chromosome and verified their specificity using PCR.Finally,38 SSR markers were tetraploid Th.elongatum1E chromosome-specific.In summary,a homozygous 1BS·1EL translocation line with high resistance to stripe rust was generated and identified in this research.In addition,the alien 1E specific SSR molecular markers were developed.The result will help mapping the stripe rust resistance gene on the 1E chromosome,as well as the creation and breeding utilization of small fragment translocation lines with stripe rust resistance in the future.