Abstract
In experiments to determine the cause of citrus blight (CB), a decline of unknown cause, subtraction hybridization was done using leaves and fibrous roots of an affected tree. Clones were identified that had similarities to Raspberry bushy dwarf virus (RBDV), the only known member of the genus Idaeovirus. The clones covered a 1555-base pairs region similar to RNA-2 of RBDV including 595 nucleotides of the 3' end of an open reading frame (ORF) that was 60% identical in amino acids to the movement protein of RBDV and a 835-nucleotide ORF that was 65% identical in amino acids to the coat protein of RBDV. RBDV is seed and pollen transmitted and is symptomless in some Rubus species. In more sensitive Rubus species, it causes a yellows disease, but only causes bushy dwarf disease with mixed infections of the aphid-borne Black raspberry necrosis virus. The sequence of the putative citrus Idaeovirus (CIV) was used to make primers for RT-PCR. Based on RT-PCR assays, the virus appears to be unevenly distributed in citrus and is present in low concentrations, making it difficult to determine whether a given tree is infected. Investigations continue to determine if CIV is associated with CB or any other disease of citrus either singly or in mixed infections with other viruses.
