Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 26, 2003
Publication Date: April 1, 2004
Citation: Faggioli, F., Pasquini, G., Campobasso, G., Widmer, T.L., Quimby Jr, P.C. 2004. Molecular identification of a new member of the clover proliferation phytoplasma group (16srvi) associated with centaureae solstitialis virescence in italy.. European Journal Of Plant Pathology. 110:353-360
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. Chemicals can manage YST but because of economic and environmental issues other control methods are sought. Malformed YST plants displaying numerous distorted, enlarged, and flatted shoots and aborted flowers were observed in central Italy. When a portion of the genetic material (DNA) was analyzed it was found to be similar to the DNA of an organism belonging in a group called phytoplasmas that also attack elm trees and eggplant. The original intent was to find an organism that could be used as a biological control agent that is specific towards YST. However, since this organism is very similar to ones described to attack elm trees and eggplant it is unlikely this agent will be pursued for this purpose. This research will benefit scientists who are looking for biological control agents by providing documentation on this previously undescribed microorganism attacking YST.
In the United States, yellow starthistle (Centaurea solstitialis) is an annual invasive weed with Mediterranean origins. Malformed plants displaying witches'-broom, fasciations, abortion of buds and flower virescence symptoms were observed in central Italy. Attempts to transmit the causal agent from the natural yellow starthistle host to periwinkle by grafting, resulted in typical symptoms in the periwinkle of a phytoplasma, such as yellowing and shortening of internodes. The detection of phytoplasmas was obtained from both symptomatic yellow starthistle and periwinkle by the specific amplification of their 16S-23S rRNA genes. PCR amplification of extracted DNA from symptomatic plant samples gave a product of expected size. Asymptomatic plants did not give positive results. An amplicon obtained by direct PCR with universal primers P1/P7 was cloned and sequenced. The homology search using CLUSTALW program showed more than 99% similarity with Illinois Elm Yellows phytoplasma from Illinois (U.S.) and 97% with Brinjal Little Leaf phytoplasma from India. Digestion of the nested-PCR products with restriction enzymes led to RFLP patterns referable to those described for phytoplasmas belonging to the clover proliferation (16SrVI) group. Since this is a previously undescribed disease, the name Centaurea solstitialis virescence has been tentatively assigned to it. This is a new phytoplasma with closest relationships to Illinois Elm Yellows and Brinjal Little Leaf, but distinguishable from them considering 16SrDNA homology, the different associated plant hosts, and the geographical origin.