First report of Uromyces rumicis on Rumex crispus in Canada

Rumex crispus L. (curled dock) is a noxious weed in both grasslands (mainly pastures) and arable lands, but is also an early colonizer of many disturbed areas in lowland and upland regions. Rumex crispus is of agricultural significance because it competes with sown or native pasture and crops species and occupies areas that could be utilized by more palatable crop species. Rumex crispus can grow on almost all soil types but less often on peat and acidic soils. The range of altitude to which the species has become adapted varies from sea level to 3,500 m (Zaller 2004). This plant species has Eurasian origin and is widely distributed through temperate regions of North America as an introduced species. There is no previous rust report on R. crispus in Canada. On other Rumex species two Puccinia species viz. Puccinia acetosae (Schumach.) Körn., and P. ornata Arthur & Holw., have been previously reported from Canada (Farr & Rossman 2022). During the recent field survey from southern British Columbia, Langley, heavily rust infected leaves of R. crispus were observed. Uredinia and telia were present on both sides of the leaf mainly on the lower side. Uredinia early exposed, brown, and pulverulent. Urediniospores were obovoid, ellipsoid or oblong, measuring 20-28 × 17-23 µm. Urediniospore walls are yellowish brown to brown, 1.5-2 µm thick; covered in evenly distributed echinulae, spaced 2 to 3 μm apart, with smooth (non-echinulate) patches at the equator of the urediniospores. Urediniospores with 2- (mostly 3 and less often 2) germ pores, usually supraequatorial (at the upper part of the spore), or distributed irregularly (scattered), or 2 germ pores supraequatorial, one equatorial or all germ pores equatorial, germ pores covered with flat papilla. Telia similar to the uredinia, dark brown. Teliospores more or less globoid, ellipsoid, broadly ellipsoid, obovoid or oblong, 25--36 × 15-23 µm, brownish yellow to brown, smooth, 2-3 um thick, with apical or sup-apical germ pore, covered with a hemispherical, yellowish papilla, pedicels colorless, short. The above-mentioned characters fit Majewski's (1977) description for Uromyces rumicis (Schumach.) G. Winter. To confirm identity, the first 903 bp of the 5' end of the 28S rDNA of the above specimen was amplified following protocols of Aime (2006) and Aime et al. (2018) (GenBank accession no. ON166844). BLAST queries of the sequence shared 99.56% identity (900/903) with U. rumicis (GenBank accession no. KY764197). To our knowledge this is the first report of U. rumicis from Canada (Farr and Rossma 2022). There is only one previous published report of this rust species in North America made by French (1989) who reported U. rumicis on R. crispus from California. Uromyces rumicis is quite common on Rumex species including R. crispus in Eurasia and has also been reported on this host from Africa (Farr and Rossman 2022). It appears that the above rust fungus species may have been introduced to the North America by accompanying its host plant. A voucher specimen of infected R. crispus with U. rumicis was deposited at Arthur Fungarium (PUR) under the accession number PUR N24014. Uromyces rumicis is a heteromacrocyclic rust with aecial state on Ranunculaceae members especially Ranunculus ficaria L. This species is another introduced plant in North America. However, there is no report of the aecial state of this rust in North America to date. Existence of only two reports of U. rumicis in California and British Columbia, making it likely that U. rumicis became established in the West Coast of North America probably no earlier than the second half of the 20th century.