Transferring the stripe rust resistance genes Yr5 and Yr15 to the bread wheat using marker-assisted backcrossing

Abstract

Yellow rust is one of the most significant wheat diseases worldwide, particularly in Iran. The cultivar Roshan, which is widely cultivated in Iran, is susceptible to this disease despite its excellent agronomic traits. Farmers in this area are understandably concerned about the damage caused by yellow rust. The aim of this study is to enhance the resistance of the cultivar Roshan against yellow rust. Given that the genes Yr5 and Yr15 are recognized as the most effective resistance genes against yellow rust in Iran, these genes were transferred to the cultivar Roshan using the marker-assisted backcrossing (MAB) method. To achieve this, the cultivar Roshan was crossed with Yr15/6∗Avocet and Yr5/6∗Avocet lines as the Yr15 and Yr5 donors, respectively. The F1 progeny was backcrossed with the cultivar Roshan, producing the BC1F1 generation. In the BC₁F₁-BC₅F₁ generations, heterozygous genotypes carrying the resistance gene were identified using specific markers, and subsequent backcrosses with the recipient parent were performed. The BC₅F₂ generation was created through self-pollination of the BC₅F₁ generation and consisted of three genotypes: homozygous susceptible plants, heterozygous plants, and homozygous resistant plants. The homozygous resistant genotypes were identified as rust-resistant near-isogenic lines (NILs^Yr5 and NILs^Yr15). To pyramid the Yr5 and Yr15 genes into the Roshan background, BC₃F₁ plants carrying Yr5 were crossed with BC₃F₁ plants carrying Yr15, producing NILF₁ plants, which were then backcrossed with the cultivar Roshan. In the next step, the obtained generation was selfed, and homozygous resistant genotypes for both Yr5 and Yr15 were selected. In general, we developed three NILs, including NILs^Yr5, NILs^Yr15, and NILs^Yr5+Yr15, for stripe rust resistance, which have the potential to replace the cultivar Roshan.