Submitted to: American Phytopathological Society Abstracts
Publication Type: Other
Publication Acceptance Date: 7/30/2005
Publication Date: 8/1/2005
Citation: Phytopathology 95:S14
Technical Abstract: Russian knapweed (RK, Acroptilon repens) is a rangeland weed pest in the western United States. A rust disease caused by Puccinia acroptili occurs on RK in North America but does not control it. Recently, a rust fungus was collected in Turkey from severely damaged RK; greenhouse tests confirm its potential as a candidate for biological control. Teliospores are two-celled, and urediniospores are one-celled with 3 more-or-less equatorial germ pores. For these reasons and because the host is A. repens, we have identified the fungus tentatively as P. acroptili. Severe disease developed both on stems and leaves, particularly after teliospore inoculations. Notable with teliospore inoculations is simultaneous development of both orange-colored pycnia and uredinoid pustules. Crosses between pycnia resulted in development of uredinoid aecia in approximately 50% of the cases. Ribosomal DNA sequences indicate pycnia were derived from teliospore inoculations, thus suggesting that this rust fungus is macrocyclic and autoecious. This also may be the first verification of pycnia and aecia from P. acroptili, which according to Savile (Can. J. Bot. 48: 1567-84, 1970), are unknown. Future research will involve comparisons with North American isolates of P. acroptili, including pathogenicity tests and molecular analyses.