Pyrenophora Species Associated with Barley and Wheat in Japan

Fungal pathogens of the genus Pyrenophora pose significant threats to barley and wheat production worldwide. Pyrenophora tritici-repentis has long been recognized as the causal agent of yellow spot disease in wheat in Japan. However, preliminary molecular data have suggested the involvement of an additional Pyrenophora species. To clarify the species diversity and phylogenetic relationships of Pyrenophora species on Poaceae plants in Japan, a total of 13 isolates, obtained from symptomatic barley and wheat, along with 37 isolates from culture collections, were analyzed using a concatenated dataset of ITS, LSU, rpb2, and gapdh gene regions. The resultant tree revealed that all examined Japanese isolates previously labeled as Py. tritici-repentis were recognized as Py. trichostoma. Furthermore, these isolates shared a toxin-producing gene. Additionally, some Japanese isolates need to have their labels corrected. These findings indicate greater diversity of Pyrenophora than previously reported in Japan and highlight the need to revise the taxonomy of Pyrenophora species.