Stem rust (Puccina graminis) identified on spring barley in the UK adjacent to infected Berberis vulgaris.
Wheat stem rust caused by the fungus Puccinia graminis f.sp. tritici is a notorious disease of wheat and barley. In western Europe, following many decades of absence the disease started to re-emerge in 2013 with sporadic wheat stem rust outbreaks reported in Germany, Sweden and Denmark. In the same year, a single wheat plant infected with stem rust was discovered in the UK, which marked the first record of the disease in over 60 years. In 2016, a much larger outbreak was recorded in Sicily. In mid-July to early August 2019, symptoms typical of stem rust were identified on approximately 20 late-sown spring barley plants in Suffolk in the UK. These infected barley plants were recorded on the edge of a field within metres of an established B. vulgaris hedgerow that was also heavily infected in the spring with orange, tube-like aecial structures typical of stem rust. DNA was extracted from infected barley stems and aecia identified on B. vulgaris leaves and the internal transcribed spacer region amplified. PCR products were sequenced and sequences deposited in Genbank (MN385566-7). A sequence alignment was then performed including 27 additional ITS sequences from various P. graminis formae speciales. Phylogenetic analysis confirmed (i) the presence of P. graminis, and (ii) that the P. graminis ITS sequences from barley and B. vulgaris infections clustered in a clade with other P. graminis formae speciales that predominantly infect wheat (Triticum aestivum) and barley (Hordeum vulgare), wild rye (Secale strictum) and couch grass (Elymus spp.), which are too similar to differentiate using gene sequence analysis. This report illustrates that stem rust can be identified late in the season on barley in the UK, most likely caused by inoculum originating on neighbouring B. vulgaris plants.