Genes for wheat stem rust postulated in German cultivars in seedling stage and their resistance in adult-plant field tests

Authors: FLATH, KERSTIN - Julius Kuhn Institute; MIEDANER, THOMAS - University Of Hohenheim; OLIVERA FIRPO, PABLO - University Of Minnesota; Rouse, Matthew; Jin, Yue

Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2018
Publication Date: 4/30/2018
Citation: Flath, K., Miedaner, T., Olivera Firpo, P., Rouse, M.N., Jin, Y. 2018. Genes for wheat stem rust postulated in German cultivars in seedling stage and their resistance in adult-plant field tests. Plant Breeding. 137:301-312. https://doi.org/10.1111/pbr.12591.
DOI: https://doi.org/10.1111/pbr.12591

Interpretive Summary: Stem rust of wheat gained high international attention in the last two decades due to the epidemics caused by Ug99 and other virulent races, but it does not occur regularly in Germany. Motivated by a regional epidemic in 2013 in Germany, we analyzed 15 spring and 79 winter wheat cultivars registered in Germany for their reaction to stem rust in seedling and adult-plant stages. In 52 cultivars, a total of five seedling resistance genes could be postulated with resistance gene Sr38 occurring most frequently, followed by Sr31 and Sr24. Resistance genes Sr7a and Sr8a occurred only in each of two spring wheat genotypes. Three cultivars had effective seedling resistance, however the resistance gene(s) could not be identified. Resistance genes Sr24 and Sr31 fully protected wheat cultivars from stem rust in the adult-plant stage. Disease responses of cultivars carrying Sr38 varied from resistance to moderate susceptibility. Two winter wheat cultivars with seedling resistance to all 13 international stem rust isolates were also fully resistant in adult-plant stage. Results from the combined seedling and adult plant tests indicated adult plant resistance to stem rust is likely present in German wheat cultivars. The information from this research will be useful for breeders to utilize the effective stem rust resistance genes in the germplasm improvement for stem rust resistance.

Technical Abstract: Stem rust of wheat (Puccinia graminis f.sp. tritici) gained high international attention in the last two decades, but does not occur regularly in Germany. Motivated by a regional epidemic in 2013, we analyzed 15 spring and 79 winter wheat cultivars registered in Germany for their resistance to stem rust in seedling and adult-plant stages. In 52 cultivars, a total of five seedling resistance genes could be postulated with Sr38 occurring most frequently (N=29), followed by Sr31 (N=9) and Sr24 (N=7). Sr7a and Sr8a occurred only in each of two spring wheat genotypes. Three cultivars had effective seedling resistance, however the resistance gene(s) could not be identified. Resistance genes Sr24 and Sr31 fully protected wheat cultivars from stem rust in the adult-plant stage. Disease responses of cultivars carrying Sr38 varied from resistance to moderate susceptibility. Two winter wheat cultivars with seedling resistance to all 13 international isolates were also fully resistant in adult-plant stage. Mean stem rust severity of cultivars with no postulated seedling resistance genes ranged in the field from 2.7 to 41.5%, nine of which were significantly less diseased than the most susceptible cultivar. This suggests adult plant resistance to stem rust may be present in German wheat cultivars.