Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2002
Publication Date: 8/1/2002
Citation: Widmer, T.L., Castlebury, L.A., Rossman, A.Y. 2002. First report of phoma exigua on centaurea solstitialis [asteraceae] in russia. Plant Disease 86:922
Interpretive Summary: Centaurea solstitialis, common name yellow starthistle (YST), is a noxious weed that has invaded the United States from the Mediterranean region. It is a serious pest of pastures, rangelands, croplands, natural areas, and recreational areas. It is a prime candidate for using natural enemies as a method for control because other control strategies, such as herbicides, have been inadequate or too costly. A fungus identified as Phoma exigua was isolated from dead YST plants in Russia. When YST was transplanted to soil containing this fungus, a death of 80 and 93% of the plants resulted after 7 days, depending upon the amount of the fungus added to the soil. Therefore, this fungus has the potential to reduce the spread of this weed by a natural way without the use of chemicals.
Technical Abstract: Phoma exigua Desm. (teleomorph Didymella exigua (Niessl) Sacc.) was isolated near Krasnodar, Russia from Centaurea solstitialis L. (yellow starthistle [YST]) plants with necrosis of the crown. The fungus was identified using morphological and cultural characteristics (1,2) and confirmed by sequencing the complete ITS region of the nuclear rDNA (AY089978). Phoma exigua is a relatively common, soil-borne fungus that is weakly pathogenic on a diverse range of primarily dicotyledonous plants throughout the world (1). It has never been reported previously on members of the genus Centaurea L. Native to eastern Europe, YST is a noxious weed in North America for which this fungus is being investigated as a potential biological control agent. Pathogencity studies resulted in a mortality of 80 and 93% within 7 days when 1-week old seedlings were transplanted in soil infested with P. exigua-colonized wheat seed at rates of 6.7 and 10% (v/v), respectively. The isolate of Phoma exigua has been deposited as a dried specimen (BPI841766) and a living culture at CBS. (1) G. Morgan-Jones and K.B. Burch. Mycotaxon 32:477, 1988. (2) H.A. Van Der Aa et.