Transferring the Psathyrostachys huashanica 5Ns chromosome into wheat genetic background to enhance powdery mildew resistance

Disease resistance is crucial for minimizing agricultural inputs and safeguarding food supply to solve world hunger. The genetic diversity of wild relatives provides a valuable resource for enhancing the disease resistance and yield of crops such as common wheat (Triticum eastivum). Psathyrostachys huashanica (2n = 2x = 14, NsNs) is a valuable wild germplasm for wheat improvement because of its resistance to various diseases and abiotic stresses. Here we report that WPh13-2, a wheat-P. huashanica distant hybridization progeny, exhibited exceptional resistance to wheat powdery mildew (PM) at both seedling and adult stages. Genome in situ hybridization (GISH) revealed a karyotype of 2n = 42 = 21 II in WPh13-2 that carries one pair of alien chromosomes from P. huashanica. Preliminary evidence from fluorescence in situ hybridization (FISH) and molecular markers analysis indicated that P. huashanica 5Ns chromosome substituted the wheat 5D chromosome in WPh13-2. The SNP array analysis demonstrated that the genotypes of most loci on the 5D chromosome of WPh13-2 were the same as in P. huashanica, but different from those of the wheat parent, confirming the replacement of the 5D chromosome with the 5Ns chromosome in WPh13-2. Analysis of PM resistance in the F2 population (MX169 × WPh13-2) located the PM resistance gene(s) on 5Ns chromosome. Finally, a 5Ns chromosome specific kompetitive allele-specific (KASP) marker was developed for molecular assistant selection of 5Ns chromosome. WPh13-2 will be a promising bridging germplasm for introgression of the PM resistance gene(s) into wheat breeding programs.