First Report of Rust Disease Caused by Puccinia nishidana on Cirsium setidens

Abstract

Cirsium setidens Nakai, endemic to Korea, is a perennial plantbelonging to the Compositae. It is distributed mainly in mountainousregions throughout the Korean Peninsula. As young leaves andshoots of the plant are edible as well as medicinal, private gardenersin mountainous villages in Korea have frequently grown it for self-consumption. Recently, commercial cultivation of this vegetablehas developed for supplying fresh produce to urban consumers. InSeptember 2009, severe outbreak of rust disease occurred on C.setidens cultivated in an experimental farm of Gangwon AgriculturalResearch & Extension Services in Pyeongchang, Korea. The rustinfections of the plant have been noticed since 1992 (HDS,unpublished data). The rust fungus produced urediniospores withindark brownish pustules, mostly on the lower surface of the infectedleaves during summer (Fig. 1A). From August to September,blackish brown pustules bearing teliospores began to produce (Fig.1B). As the disease progressed, the symptoms of yellowing andnecrosis on the leaf lesions became more intense. The voucherspecimens were deposited in the herbarium of Korea University,Seoul, Korea.The morphology of the causal pathogen was examined with LMand SEM. Uredinia were mostly hypophyllous, erumpent, darkbrownish, circular to irregular in shape (Fig. 1C). Urediniosporeswere broadly obovoid to subglobose, yellow-orange to goldenbrown, echinulate, 25−30×23−25 µm (including wall thickness)(Fig. 1E & G). Telia were mostly hypophyllous, subepidermal atfirst, later erumpent, blackish brown (Fig. 1D). Teliospores werebroadly ellipsoid, chestnut-brown, 35−40×27−30(−33) µm, two-celled with slightly verrucose cell walls and a usually broken,colourless pedicel (Fig. 1F & H). A germ pore of the upper cell wasmostly apical, and that of the lower cell was located near septum.There was a slight umbo over each germ pore. Based on thesemorphological characteristics, this fungus was identified asPuccinia nishidana Henn., as described by Hiratsuka et al. (1992)and Zhuang (2003) .Genomic DNA was extracted from teliospores of the driedherbarium specimens (KUS-F24576, F24870). PCR amplificationand sequencing of both ITS2 region of rDNA and D1/D2 region of28S rDNA were performed using the primers Rust2inv and LR6 asdescribed by Aime (2006). The resulting sequences (approximately1400 bp) of the two isolates were identical to each other, anddeposited in GenBank (HM022140, HM022141). However, asthese were the first sequences for P. nishidana, molecular confir-mation for the identification could not be made in the present study. Puccinia nishidana is widely distributed in Japan, China, Russiaand Korea (Hiratsuka et al., 1992) and about 30 species of the genusCirsium have been reported as its host plants, but there has been noprevious record of P. nishidana on C. setidens (Farr and Rossman,2010).T herefore, this si the first reportof rust infection byht e funguson this plant. The occurrence of rust disease on C. setidens will havesignificant impact on the commercial production of the vegetableand effective control methods will be required.