First Report of Gladiolus Rust Caused by Uromyces transversalis in Merida, Venezuela

Abstract

In December of 2016, rust sori were observed on leaves of gladiolus plants (Gladiolus sp.) in a garden located in the National Forest Products Laboratory, Faculty of Forestry and Environmental Sciences, University of Los Andes, Merida, Venezuela. All gladiolus plants in the garden were infected. The uredinia were bright orange, variable in shape from globose to ovoid, coalescing transversely across the leaf. The urediniospores were hyaline to yellow gold, ovate to oblong, echinulate, and measured 15 to 26 × 15 to 20 μm with a wall 1.5 to 2.5 μm thick. Telia were not observed. Based on uredinial morphology, the pathogen was identified as Uromyces transversalis (Thum.) G. Winter (Hernandez 2004). Molecular analyses were performed to confirm identification of the rust. Genomic DNA was extracted from symptomatic gladiolus leaves, and the first 680 bp of the nuclear ribosomal large subunit (28S) were amplified and sequenced following protocols described in Aime (2006). The Venezuelan isolate shared 100% identity with U. transversalis BRIP56045 (GenBank accession no. KM249863; McTaggart et al. 2016) in BLAST analyses. A voucher specimen has been deposited in the Arthur Fungarium, Purdue University (PUR N16743) and sequence data in GenBank (MF374730). Gladiolus rust is capable of causing severe disease on up to 100% of plants being grown for flower production (Blomquist et al. 2007; Rodriguez-Alvarado et al. 2006). U. transversalis has been reported on Gladiolus sp. in parts of Africa and Europe, Australia, New Zealand, Argentina, Brazil, Martinique, and Mexico (Blomquist et al. 2007; Hernandez 2004). To our knowledge, this is the first report of U. transversalis causing gladiolus rust in Venezuela. The country must take quarantine control measures as well as eradication programs for this pathogen before it is spread throughout the national territory.