Abstract
Multiple species of defective RNAs (D-RNAs) were found in citrus plants infected with several Israeli and Florida isolates of the citrus tristeza virus (CTV). These D-RNAs consist of 5' and 3' terminal fragments of the CTV RNA and lack most of the genetic information contained in the CTV genome. The overall organization of the CTV-specific D-RNAs is similar to the structure of defective-interfering RNAs (DIs) found in other plant viruses. These DIs are known to modulate symptom expression in infected plants mitigating or delaying development of the virus infection. Investigations aimed at finding possible association of the CTV-specific D-RNAs with particular symptoms in different citrus hosts are under way.
