First Report of Uromyces acuminatus on Honckenya peploides, the Endangered Seabeach Sandwort.

Abstract

Honckenya peploides (L.) Ehrh. (Caryophyllaceae), commonly known as seabeach sandwort, is a species of special concern in Connecticut (4). Nearly an entire population of H. peploides in New London County, CT was found to be severely infected by the aecial stage of a rust fungus in June of 2008. Representative plants in the population were infected with aecia on more than 50% of the leaves. Aecia were amphigenous, gregarious, cupulate, pulverulent, yellowish, and erumpent with a hyaline to whitish peridium having a lacerate, somewhat recurved margin. Peridial cells were rhomboidal, 26 to 31 × 25 to 29 μm, smooth to finely verrucose. Aeciospores were globose to ellipsoid, 23.5 to 29 × 20.5 to 22 μm, hyaline to pale yellowish with a verrucose surface and hyaline walls 1.5 to 2 μm thick. Morphological characters corresponded to a reference specimen (BPI 000105) of the aecial stage of Uromyces acuminatus Arthur from Nova Scotia, as well as published descriptions (1,2). Subsequently, telia of U. acuminatus were discovered on Spartina patens (Aiton) Muhl. (Poaceae) in May of 2009 in New London County, CT. Telia were adaxial, intercostal, scattered to gregarious, linear and at times elongate, dark brown to black, pulverulent, and erumpent. Teliospores were obovate to ellipsoid with rounded to acuminate apices rarely having two points, 30 to 41 × 19 to 24 μm, with a smooth surface and brownish-yellow to brown walls 9 to 14 μm thick at apex, which is sometimes paler, and 1 to 3 μm thick laterally, pedicels with a portion persisting on the teliospore that is up to 82 μm long and brownish-yellow. The ITS2 and 5' region of the 28S rDNA (998 bp) from the rust on H. peploides (GenBank Accession No. GU109282, BPI 879300) and the rust on S. patens (GenBank Accession No. GU058008, BPI 879285B) were sequenced to confirm the identification of U. acuminatus on H. peploides with the resulting sequences identical. U. acuminatus is widespread in the eastern United States and Canada (1-3). The telial stage is found on Spartina spp., while the aecial stage is found on numerous taxa including members of the Asparagaceae (formerly Ruscaceae, Liliaceae), Caryophyllaceae, Polemoniaceae, and Primulaceae (1-3). Puccinia arenariae (Schumach.) G. Winter, previously reported from H. peploides (4), is microcyclic and stages 0, I, and II are unknown. To our knowledge, this is the first report of U. acuminatus on the genus Honckenya. This report has significance to natural resource conservation managers and scientists working in endangered plant habitats because H. peploides and H. peploides subsp. robusta are listed as plants of special concern or endangered/extirpated in Connecticut, Maryland, New Hampshire, and Rhode Island (4).