Molecular screening of Septoria tritici blotch resistance genes in European bread wheat cultivars using validated gene-specific SSR markers

Abstract Zymoseptoria tritici , the causal agent of Septoria tritici blotch (STB), poses a major threat to wheat production in temperate regions worldwide. This study aimed to determine the distribution of 15 known Stb resistance genes in 60 bread wheat cultivars from Serbia, Croatia, France, Italy, Romania, Hungary, and Mexico using validated gene-specific simple sequence repeat (SSR) markers. Genomic DNA was extracted from 35-day-old seedlings and subjected to PCR amplification using 15 Stb -linked SSR markers. The presence of target alleles was confirmed via 2% agarose gel electrophoresis. Results showed that Stb1 was present in all genotypes (60/60 = 100%), highlighting its widespread use. The 44.1% (60/136) gene detection rate was recorded for Stb1 ; in contrast, Stb9 and Stb16 were not amplified in any sample, suggesting their absence within the evaluated germplasm. Other frequently detected genes included Stb12 (33.3%), Stb14 (23.3%), and Stb4 (15%). Genes like Stb2 , Stb3 , and Stb6 were identified in only 5%, 5%, and 3.3% of genotypes, respectively. The French cultivar ‘Falado’ possessed the highest number of resistance genes (7), followed by ‘Cellule’, ‘Solindo’, ‘Sofolk’, and Serbian cultivars ‘NS Epoha’ and ‘NS Grivna’ with five genes each. These results support gene pyramiding as a strategy for durable resistance. In conclusion, while Stb1 remains predominant, the lack of diversity increases vulnerability to resistance breakdown. Underutilized genes such as Stb6 , Stb8 , and Stb17 offer potential for future resistance breeding. The study emphasizes integrating SSR-based screening with advanced tools like GWAS and functional genomics to enhance marker-assisted selection and promote sustainable wheat improvement.