New resistance in old places: resistance to the Ug99 race group of Puccinia graminis f. sp. tritici in wheat intra/inter-generic hybrids and historic germplasm

Wheat stem rust caused by the rust fungus, Puccinia graminis f. sp. tritici, threatens global wheat (Triticum aestivum) production. New races originating in Eastern Africa have overcome many existing stem rust resistance genes. The W. J. Sando collection of wheat intra/inter-generic hybrids is a valuable source of stem rust resistance. The entire collection was characterized for seedling stem rust resistance to 8 races of the stem rust pathogen and cytogenetic analysis was performed on select lines. Several accessions are postulated to contain new sources of resistance. Full screening results are displayed in Supplementary Table S1 and the pedigrees of 29 resistant lines are displayed in Supplementary Table S2. South African accession PI 410954 displayed strong resistance to stem rust race TTKSK at the seedling stage and under field conditions. The source of new resistance was located and material suitable for integration into modern spring wheat breeding programs was produced.