Marker-Assisted Development and Evaluation of Near-Isogenic Lines for Broad-Spectrum Powdery Mildew Resistance Gene Introgressed into Different Genetic Backgrounds of Wheat.

At present, most of released wheat cultivars or breeding lines in China are susceptible to powdery mildew () (caused by f. sp. , ), so there is an urgent need to rapidly transfer effective and broad-spectrum resistance genes into elite cultivars/lines. Near-isogenic lines (NILs) with short target gene region are very important in molecular breeding and map-based cloning and can be developed by combining marker-assisted selection and conventional phenotypic identification. However, no gene NILs were reported by using this method in the previous studies. A new broad-spectrum dominant resistance gene , derived from the Chinese wheat breeding line KM2939, conferred high resistance to at both the seedling and adult stages. In this study, with the aid of forward and background selection (FS and BS) using molecular markers, the gene was introgressed into three elite susceptible commercial cultivars Shimai 15, Shixin 828, and Kenong 199 through the back-crossing procedure. With the appropriate backcrossing generations, selected population sizes and marker number for BS, the homozygous resistant BCF NILs of gene in the three genetic backgrounds with the highest recipient genome composition of about 99%, confirmed by simple sequence repeat markers and 660K single nucleotide polymorphic array, were developed and evaluated for the powdery mildew resistance and agronomic traits. The different resistance and similar or improved agronomic performance between NILs and their corresponding recurrent parents indicated their potential value in the marker-assisted breeding of the gene. Moreover, the development of four flanked diagnostic markers (CFD81, BWM25, BWM20, and BWM21) of the gene can effectively assist the forward selection and accelerate the transfer and use of this resistance gene.