Recovery of orange stem pitting strains of Citrus Tristeza Virus (CTV) following single aphid transmissions with Toxoptera citricida from a Florida decline isolate of CTV

J. H. Tsai, Y. H. Liu, J. J. Wang, R. F. Lee

Abstract


CTV isolate T66a is an Aphis gossypii transmitted sub-culture of field isolate T66 which was originally collected from a rapidly declining sweet orange ( Citrus sinensis (L.) Osb) on sour orange (C. aurantium L.) rootstock in the Fort Pierce area in 1985. Isolate T66a causes moderate vein clearing and stem pitting in the CTV-sensitive indicator plant Mexican lime (C. aurantifolia (Christm.) Swing.), decline on sweet orange on sour orange rootstock, and seedling yellows and stunting on sour orange seedlings. It does not cause stem pitting on sweet orange or grapefruit (C. paradisi Macf.). A single plant infected with Florida T66a isolate was used as the source for 1224 single aphid transmission (SAT) attempts using Toxoptera citricida between 1996-1998; 79 SAT sub-isolates were recovered. By the use of differential ELISA assays, about 25% of the SAT T66a sub-isolates did not react with MCA13 and were considered mild, whereas the remainder reacted with MCA13 and were considered severe. The overall SAT rate using T. citricida was about 6.5% with no noticeable difference in the ability to transmit among the alate, apterous, or nymph stages. Fortytwo SAT sub-isolates were maintained in the pineapple sweet orange seedling receptors in the greenhouse at Lake Alfred; nine of these sub-isolates express mild to moderate stem pitting in the sweet orange hosts. Further biological and molecular characterization of the SAT sub-isolates is now underway.

Keywords


strain differentiation; elisa; serology; indicator plants

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283