Molecular Identification of a New Member of the Clover Proliferation Phytoplasma Group (16SrVI) Associated with Centaurea Solstitialis Virescence in Italy |
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Authors: | Francesco Faggioli Graziella Pasquini Valentina Lumia Gaetano Campobasso Timothy L. Widmer Paul C. Quimby Jr |
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Affiliation: | (1) Istituto Sperimentale per la Patologia Vegetale, Rome, Italy;(2) European Biological Control Laboratory, USDA-ARS, Via Colle Trugli No. 9, 00132 Rome, Italy;(3) European Biological Control Laboratory, USDA-ARS, Campus International de Baillarguet, CS 90013, Montferrier sur Lez, 34988 St. Gely du Fesc CEDEX, France |
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Abstract: | 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 of a phytoplasma, i.e. 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 (ILEY) phytoplasma from Illinois (United States) and 97% with Brinjal little leaf (BLL) phytoplasma from India. Digestion of the nested-PCR products with restriction enzymes led to restriction fragment length polymorphism patterns referable to those described for phytoplasmas belonging to the clover proliferation (16S-VI) 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 ILEY and BLL, but distinguishable from them on the basis of 16S rDNA homology, the different associated plant hosts and their geographical origin. |
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Keywords: | 16S-23S rRNA weeds yellow starthistle |
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