First Report of Puccinia lagenophorae on Senecio vulgaris in Pennsylvania.

Abstract

Common groundsel (Senecio vulgaris L.), is an aster native to Eurasia and is now a common weed in gardens, roadsides and vacant lots worldwide. In 2001, Scholler and Toike were first to report that common groundsel was a host for the rust fungus Puccinia lagenophorae Cooke in North America (Scholler and Toike 2001). This report from California was followed by reports of P. lagenophorae infections on common groundsel in New York, Oklahoma, and Oregon (Little-field et al. 2005). In 2007, Bruckart et al. published the first report of this host-pathogen combi-nation in Canada (Bruckart et al. 2007). To our knowledge, there are no published reports of P. lagenophorae on common groundsel in Pennsylvania (Farr and Rossman 2022). In May 2022, symptomatic common groundsel plants were observed in Biglerville, Adams Co., southern Penn-sylvania (N 39.9268047, E 77.2473878). Host plants exhibited conspicuous aecia on deformed stems (Fig. 1). Disease symptomology and morphology were consistent with P. langenophorae (Scholler and Toike 2001). P. lagenophorae is an autoecious rust that forms aecia and telia, but only aecia are typically formed on Senecio spp.; telia were not noted during our observations. Aecia were orange, cup-shaped, bordered by fragmented recurved peridia (Fig. 1), and they had mean diameters 262.9 ± 20.9 X 175.2 ± 22.2 μm (n = 20). Aeciospores were orange, oval, with mean diameters of 16.5 ± 0.97 X 11.5 ± 1.08 μm (n = 20). Fungal DNA was extracted from symptomatic stems. Polymerase chain reaction and sequencing of the 28S region of the nuclear ribosomal DNA repeat were conducted with primers Rust2inv and LR6 following protocols in Aime (2006). The sequence shared 100% identity (909 / 909 bp) with 8 sequences of P. la-genphorae in GenBank, including one on Ozothamnus cordatus from Perth, Western Australia, Australia (KF690699), vouchered in the Queensland Plant Pathology Herbarium (BRIP 57770), Brisbane, Queensland, Australia. A voucher specimen has been preserved in the Arthur Fungari-um at Purdue University (PUR N24039) with corresponding 28S sequence (GenBank accession OP718536).