Incidence of Citrus tristeza virus in Chile and Biological and Serological Characterization of 100 Isolates

Abstract

A survey was performed from 1999 to 2002 in the main citrus regions (13,551 ha) of Chile to estimate the Citrus tristeza virus(CTV) incidence. One thousand three hundred and twenty-three commercial citrus orchards were visited and 90,267 trees were observed for symptoms, sampled and analyzed by DAS-ELISA and tissue print-ELISA using 3DF1 and 3CA5 monoclonal antibodies. In this survey stem pitting symptoms were detected on CTV-infected grapefruit and Mexican lime trees grown in small orchards located in the Pica Oasis where the CTV incidence was 17.2%. In central Chile, where the main commercial orchards are located, CTV incidence ranged from zero to 0.37%. The average incidence of CTV in Chile was estimated at 0.38%. From this survey 100 CTV isolates representative of different hosts and geographical origins were selected and inoculated on sweet orange and/or Mexican lime and conserved in a collection kept in screenhouse facilities. The isolates in the collection were biologically and serologically characterized. Severe CTV isolates were found in Region I (where Pica Oasis is located). Serological characterization was done by DASI-ELISA using 12 different monoclonal antibodies, including MCA 13. Eight different serogroups were detected, two of which included CTV isolates which yielded a positive MCA 13 reaction.