Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.). To diversify stripe rust-resistant resources for wheat breeding programs, a CIMMYT synthetic wheat line CI110 was identified to be resistant to 28 isolates of Pst, including 6 Chinese prevalent races CYR28-CYR33. Genetic analysis indicated that a single dominant gene was responsible for the stripe rust resistance in CI110, temporarily designated YrC110. A molecular map, harboring YrC110 and 9 linked SSR markers, was constructed through simple sequence repeat (SSR), and bulked segregant analysis. These linked markers and YrC110 were assigned on the short arm of chromosome 1B using the Chinese Spring nullisomic-tetrasomic and ditelosomic stocks. Gene postulation based on seedling reaction patterns to 30 Pst isolates suggested that the resistance gene YrC110 seemed different from the other known resistance genes tested, such as Yr9, Yr10, Yr15, Yr24, and Yr26/YrCH42. Four SSR markers Xbarc187150, Xgwm18227, Xgwm11223, and Xbarc240292 distinguished YrC110 from Yr10, Yr15, Yr24, and Yr26/YrCH42, and could be used as diagnostic ones for YrC110 in wheat resistant breeding programs against stripe rust.

The objective of this study was to characterize yellow (stripe) rust resistance gene(s) in 52 commercial wheat cultivars from Yunnan Province in China, and to provide information for their rational deployment in field. Seedlings of wheat cultivars were inoculated with 25 differential isolates of Puccinia striiformis from foreign and home to postulate resistance genes to yellow rust, and then validated by pedigree. There were 10 probable resistance genes characterized in these cultivars, in which, Yr9 was most commonly postulated to be present in thirteen cultivars. Yr21, the second, was present in four cultivars. Yr8, the third, were present in three cultivars. Yr6, Yr17 and Yr26, the fourth, was present in two cultivars respectively. The other gene(s) such as, Yr2+YrA, Yr7 and Yr27, were only present in single cultivar(s); unknown gene(s) or gene(s) combination(s) were present in 22 cultivars. One cultivar (Yunmai 42) had no resistance gene tested in this study. Cultivars such as Yunmai 52, Mian 1971-98, Kunmai 4, and Yunmai 56 carried effective genes and can be popularized mainly; Yr9 should be planted with other Yr genes. In the meantime other effective genes should be introduced to realize gene diversity for controlling wheat yellow rust. Yunmai 42 should be reduced to avoid rust breakout. Unknown gene cultivars should be utilized and be researched deeply.