Outbreak of yellow rust on triticale in Serbia

Triticale (xTriticosecale Wittmack) is a hybrid obtained by crossing wheat (Triticum sp.) and rye (Secale sp.). Triticale possesses favorable agronomic characteristics compared to wheat and rye, including suitability for cultivation in poor and acidic soils or under cold conditions. The causal agent of yellow rust in triticale (P. striiformis f. sp. tritici, Pst) is one of the pathogens responsible for significant yield and quality losses. An aggressive race of Pst, first discovered in Europe in 2006 on the island of Bornholm on triticale, has become common in widely grown triticale varieties in Germany and Scandinavia. Although the race belongs to P. striiformis f. sp. tritici, it has never been found on winter wheat varieties in Europe. The aggressive triticale race has led to yield losses of up to 100% in Scandinavia, where controlling triticale epidemics in organic production has proven challenging. It is worth noting that Pst races Warrior and Kranich, which caused significant wheat yield losses in Europe since 2011, were also detected on triticale. During the 2022/2023 growing season on locality Rimski Sanéevi (Vojvodina, North Province of Serbia) yellow rust was recorded on triticale in Serbia for the the first time. Among 280 tested triticale genotypes, 39.4% were infected with yellow rust with a disease index (Dl) exceeding 50%. Only 0.9% of genotypes were infected with yellow rust with a DI less than 10%. The remaining genotypes showed infection within the following ranges: 11% < DI < 20% (4.8%); 21% < DI < 30% (10.8%); 31% < DI < 40% (20%); and 41% < DI < 50% (24.2%). Symptoms of yellow rust disease have been observed on triticale in the form of yellow uredosori arranged in regular rows along the leaf veins. In contrast to the symptoms of yellow rust in wheat, the infection type of yellow rust on triticale is accompanied by more pronounced necrosis of the leaves during severe attacks. The dimensions of uredospores ranged from (18.7—33) to (15-28.2) um. Despite the occurrence of yellow rust on wheat in Serbia in previous years, it had not been registered on triticale until 2023. Consequently, this study provides not only information on possible sources of resistance but also highlights the need for increased attention to monitor yellow rust populations in Serbia to ensure effective control management