Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/20/2003
Publication Date: 3/1/2004
Citation: Guermache, F., Vidal, K., Widmer, T.L. 2004. In Vitro Culturing of Yellow Starthistle (Centaurea solstitialis) for Screening Biological Control Agents. Biological Control 30:330-335. Interpretive Summary: Yellow starthistle 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. Chemicals can manage yellow starthistle but because of economic and environmental issues other control methods are sought, including biological control through the use of pathogenic fungi. One of the limitations in finding new pathogenic fungi is the time it takes to screen all of the potential biological control agents. Current methods use whole plants that are infected with the fungi to test their reaction. This paper provides a quicker method to screen potential pathogens and toxins against yellow starthistle by using undifferentiated cells. A difference was observed in the cells that were infected with a pathogenic fungus compared to a nonpathogenic fungus. In addition, cells exposed to a fungal toxin gave a similar reaction to whole leaves. The primary benefit of this research is that it provides a method for the researcher to quickly screen fungi for their use as biological control agents in a more limitated space. This will eventually improve the efficacy for introducing new agents to control yellow starthistle
Technical Abstract: New chemical or biological agents are constantly being sought for control of the noxious, invasive weed, yellow starthistle (YST). Procedures were developed to produce calli of yellow starthistle on solid and liquid media. Three Murashige and Skoogs (MS) media with different additive hormones are compared for their effect on the growth of the YST calli. The most effective medium was made of MS salts supplemented with a balance of two cytokinins. A bioassay was setup to compare the reactions of the YST calli with detached leaves exposed to potential toxins. Calli were exposed to different concentrations of culture filtrates from three Alternaria alternata isolates. After 96 h, the calli exposed to 100% and 50% concentrations of the filtrate were significantly more damaged than other concentrations tested, based upon a visual rating scale. Alternaria alternata isolates did not show any difference among different isolates. After 48 h, a visual rating distinction could be made between calli treated with the pathogenic Phoma exigua and the nonpathogenic Penicillium sp. confirming that YST calli can be used to screen other potential pathogenic fungi against YST.