Transmission of Exotic Citrus Tristeza Virus Isolates by a Florida Colony of Aphis gossypii

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Abstract
A diverse group of citrus tristeza virus (CTV) isolates collected from 10 countries (Argentina, Brazil, China, Israel, Japan, Reunion, South Africa, Taiwan, and the United States) was tested for transmissibly by a Florida colony of the melon aphid, Aphis gossypii. Of 42 isolates tested, 21 were transmitted by the aphid. At least one isolate from each country was transmitted. Transmission percentages calculated for single aphid transmission ranged from 3 to 11% for some exotic isolates. Aphid-transmitted subcultures of several original source isolates that induce CTV decline, seedling yellows, and sweet orange and grapefruit stem ptting were compared for host reactions. All disease components were transmitted. Reduction of virulence of some aphid-transmitted subcultures was obtained by deliberate selection of variants in Mexican lime indicators compared with the original isolate. These results indicate that exotic CTV isolates, markedly more destructuve to citrus than CTV isolates commonly found in Florida, could be spread readily by endemic A. gossypii, if introduced.