Citrus tristeza virus: characterization of Texas isolates, studies on aphid transmission and pathogen-derived control strategies

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Title: Citrus tristeza virus: characterization of Texas isolates, studies on aphid transmission and pathogen-derived control strategies
Author: Herron, Caroline Mary
Abstract: Citrus tristeza virus (CTV ) , an economically important graft -transmissible pathogen of citrus , causes major global declines in citrus production . In the commercial citrus of the Lower Rio Grande Valley of Texas (LRGV ) , where red grapefruit on tristeza -decline sensitive sour orange rootstocks predominate , incidence of CTV is low . The efficient CTV vector , the brown citrus aphid (BrCA , Toxoptera citricida Kirkaldy ) is now established in Mexico and Florida , thus information is needed on the severity of CTV , CTV aphid transmission and the performance of transformed citrus towards CTV before T . citricida arrives in Texas so that appropriate management strategies can be selected . Biological indexing and molecular typing were performed on fifteen Texas CTV isolates . The majority of the CTV isolates tested contained the most severe CTV types known . In Florida , T . citricida were fed on crude CTV preparations in vitro and could transmit CTV to virus -free receptor plants with two CTV isolates , whereas a more highly purified CTV preparation from one CTV isolate was not transmitted by T . citricida . There were no differences in the majority of treatments in infectivity neutralizations using three CTV -derived antibodies (p25 , p27 and p20 ) . CTV p20 antibodies significantly enhanced the occurrence of CTV transmission in one test . The CTV genome of isolate H33 was sequenced using 'shot gun' methods . The H33 major component and H33 minor components were phylogenetically compared to the six other full -length CTV sequences . An untranslatable CTV coat protein gene was genetically transformed into the genome of the Texas commercial Rio Red grapefruit variety , and fifty -two independent transgenic lines were produced . CTV challenge responses by the transgenic lines were variable . Individual plants could be identified which had low virus titers by ELISA detection , a temporal decrease in virus titer , or a delay in virus titer accumulation . Comparing all wild types to all transgenic lines over every assessment revealed significant decreases in virus titer in the transgenic lines compared to that of the wild type . An RNA entity with similarities to marafiviruses was identified in a CTV infected plant . The entity appears non -graft transmissible to citrus , and non -mechanically transmissible to a range of herbaceous species .
URI: http : / /hdl .handle .net /1969 .1 /1198
Date: 2004-11-15

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Citrus tristeza virus: characterization of Texas isolates, studies on aphid transmission and pathogen-derived control strategies. Available electronically from http : / /hdl .handle .net /1969 .1 /1198 .

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