Segregation of Citrus Tristeza Virus Strains Evidenced by Double Stranded RNA (dsRNA) Analysis

Abstract

A field isolate of citrus tristeza virus (CTV), T-385, was separated from other virus and virus-like diseases by aphid transmission to Mexican lime seedlings. This isolate did not cause decline of sweet orange on sour orange rootstock under field conditions and it induced mild vein clearing and an inconspicuous stem pitting on Mexican lime. Two months after aphid transmission, one of the infected lime seedlings was used as an inoculum source to graft-inoculate 40 citron plants. Two years later, the citron plants were analysed individually for dsRNA content and up to 23 different electrophoretic profiles were found. DsRNA analysis has been repeated three times through the year and the individual patterns remained unchanged. Thirteen of these CTV sub-isolates were graft-transmitted to sweet orange seedlings and the corresponding dsRNA profiles were identical to those previously obtained from citron. All these subisolates induced mild symptoms of Mexican lime similar to those of the original isolate (T-385). These results substantiate that several CTV strains can infect a single citrus plant.