First report of Uromyces acuminatus on Honckenya peploides, the endangered seabeach sandwort

Authors: YUN, H.Y. - Iowa State University; MINNIS, A.M. - Rutgers University; Dixon, Linley; Castlebury, Lisa

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2009
Publication Date: 2/1/2010
Citation: Yun, H., Minnis, A., Dixon, L.J., Castlebury, L.A. 2010. First report of Uromyces acuminatus on Honckenya peploides, the endangered seabeach sandwort. Plant Disease. 94:279.

Interpretive Summary: Rust fungi are a very large and diverse group of parasites that attack different kinds of plants including crop and native species. Many rust fungi have complicated life cycles in which they occur on unrelated plant hosts. Accurate knowledge of the host range of a rust is important for determining how to control the disease it causes. In this research an endangered plant called seabeach sandwort was encountered with a strange rust disease. A survey of nearby plants yielded a rust fungus on marsh grass. The rust on these two different plant hosts was determined to be the same fungus; it was not previously known to occur on seabeach sandwort. This research will be used by plant pathologists and conservationists to control the rust disease that kills this endangered plant.

Technical Abstract: Honckenya peploides, commonly known as the seabeach sandwort, is a species of special concern in Connecticut. 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. Nearly all 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, 25–29 × 26–31 µm, smooth to finely verrucose. Aeciospores were globose to ellipsoid, 20.5–22 × 23.5–29 µm, hyaline to pale yellowish with a verrucose surface and hyaline walls 1.5–2 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, also known as marshgrass, 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, 30–41 × 19–24 µm, with a smooth surface and brownish-yellow to brown walls 9–14 µm thick at apex, which is sometimes paler and 1–3 µm thick laterally, pedicels with a portion persisting on the teliospore, up to 82 µm long, brownish-yellow. The ITS2 and 28S rDNA genes (998 bp) from the rust on H. peploides (GenBank accession number GU109282, BPI 879287) and the rust on S. patens (GenBank accession number GU058008, BPI 879285B) were sequenced to confirm the identification of U. acuminatus on H. peploides with the resulting sequences identical. Uromyces acuminatus is widespread in the eastern United States and Canada. The telial stage is found on Spartina spp., while the aecial stage is found on numerous taxa including members of the Caryophyllaceae, Polemoniaceae, Primulaceae and Ruscaceae. 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 as H. peploides and H. peploides ssp. robusta are listed as plants of special concern or endangered/extirpated in Connecticut, New Hampshire, Maryland and Rhode Island.