First report of rust disease caused by Puccinia elymi on Leymus chinensis in China   

Leymus chinensis (=Aneurolepidium chinense, Gramineae) is an important perennial grass species widely distributed in the eastern part of the Eurasian grassland. It has become a dominant species in the grass steppe of northeastern China. During a plant disease survey in Baicheng City, Jilin province of China, in early summer 2005, symptoms of rust disease were observed on the leaves of L. chinensis (Fig. 1).

The severity of the disease attack had notably increased by mid-August. Numerous uredinia occurred, mostly on the upper leaf surfaces. Initially scattered, they later occurred at much higher densities, often confluent, cinnamon-brown, and surrounded by the ruptured epidermis. The uredospores were ellipsoid, obovoid, or broadly ellipsoid, yellowish to golden, and measured 20-30×18-25 µm, with a thick wall up to 2-4 µm thick and 8-10 scattered germ pores (Fig. 2). Production of the teliospores was observed during late summer and autumn. Numerous telia occurred in October. Telia mostly appeared on the lower surface of leaves and sheaths. They were scattered or arranged in lines, often confluent, covered by a blackish epidermis (Fig. 3). The striking appearance of the chestnut-brown multiseptate teliospores (2 to 4-celled, mostly 3-celled) rendered this rust easily recognisable. The teliospores measured 45-90×10-18 µm, with walls 1.5 µm thick at the sides and 3-7 µm at the apex (Fig. 4). Based on the morphological characters described above, this rust pathogen was identified as Puccinia elymi (Wilson & Henderson, 1966).

P. elymi was first described on Elymus arenarius from Belgium in 1851 (Cummins, 1971). It has a wide distribution in Europe and Asia from Great Britain to China (Wilson & Henderson, 1966; Cummins, 1971; Zhuang et al., 1998). The aecia occur on Thalictrum of Ranunculaceae, and the uredinia and telia have been recorded frequently on Elymus spp. (Cummins, 1971). Other hosts affected in China are Elymus sibiricus, Roegneria sinica var. media, R. turczaninovii and Poa sp. (Zhuang et al., 1998). This rust, however, has never been recorded on L. chinensis in China or in other parts of the world. The rust species recorded so far on L. chinensis in China are Puccinia coronata, P. rangiferina, P. recondita and P. striiformis (Nan & Li, 1994).