ARS | Publication request: First Report of Puccinia Jaceae Var. Solstitialis Pycnia on Yellow Starthistle in the United States

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2006
Publication Date: October 1, 2006
Citation: Fisher, A.J., Bruckart, W.L., Mcmahon, M., Luster, D.G., Smith, L. 2006. First report of puccinia jaceae var. solstitialis pycnia on yellow starthistle in the United States. Plant Disease.90:1362.

Interpretive Summary: Puccinia jaceae is a rust fungus that infects yellow starthistle. An isolate of P. jaceae was collected in Turkey and tested to see if it would damage only YST (and not other plants). It was approved for biological control in California and was used to inoculate YST plants in 2003. This pathogen has a complex life cycle, and this is the first time that the pycnial stage was observed in the United States. The pycnial stage is necessary for mating of this fungus. This discovery of pycnia, which are tiny and hard to find, means that P. jaceae completes its life cycle in the U.S.

Technical Abstract: The rust fungus Puccinia jaceae (Otth) var. solstitialis field isolate FDWSRU 84-71 (formerly TR 84-96) was first released in California (CA) for the biological control of yellow starthistle (YST) (Centaurea solstitialis) in July 2003. This isolate was collected in 1984, east of Yarhisar and Hafik (SIVAS), Turkey. It is macrocyclic and autoecous, completing its entire life cycle on YST. Observations were made in field plots west of Woodland, CA, that had been inoculated on a monthly regime between January and June 2005. On February 22 and March 2, 2006, pycnia were observed in and around one of the plots (N 38º 42.767, W 121º53.732, and 57 meters). DNA was isolated from pycnial and uredinial samples collected from the site and used for amplification of the ITS 2 region with P. jaceae specific primers. Sequences of both samples were identical to FDWSRU 84-71. Pycnia were yellow flask shaped, and small (less than 100 'm diam.), occurring in clusters on abaxial leaf surfaces or on petioles. This is the first report of pycnia from Puccinia jaceae var. solstitialis in the United States, suggesting that P. jaceae on YST is fully functional, completing its life cycle on YST in CA.