Virion Properties

Virions are flexuous filaments mostly 650 - 675 nm x 13 - 16 nm. Virion S20w is 155 - 158S; density in CsCl is 1.31 - 1.33 g/cm³. Virions contain one molecule of linear positive sense, ssRNA. RNA is ca. 8.0 kb. Macluraviruses have a single CP species of Mr 33-34 x 10³. No lipid or carbohydrate are reported.

The amino acid sequences of macluravirus CPs show limited (14 - 23%) homology with CP sequences of some aphid-transmitted potyviruses. Macluraviruses show significant amino acid sequence homology in portions of the replicase protein with viruses in other genera of the family Potyviridae. Characteristic cytoplasmic cylindrical ("pinwheel") inclusions are present in infected cells. The macluraviruses presumably have a genome organization and replication strategy typical of viruses in the family Potyviridae.

Moderately immunogenic. No serological relationships to members of the genus Potyvirus have been found except for a weak reactions between Maclura mosaic virus (MacMV) and Narcissus latent virus (NLV) and MacMV and Bean yellow mosaic virus (BYMV). The amino acid sequence identities between MacMV and NLV CP and NIb protein are 53% and 76%, respectively.

Host Range

Both MacMV and NLV have a narrow host range, infecting species in up to 9 host families. MacMV has only been reported from the former Yugoslavia while NLV is likely to occur wherever narcissus, gladiolus and bulbous iris are grown.

Transmission

The viruses are transmitted by aphids in a non-persistent manner and are transmissible experimentally by mechanical inoculation.

• Genome sequence relatedness.

- CP amino acid sequence identity less than ca. 80%,

- nucleotide sequence identity less than 85% over whole genome,

- different polyprotein cleavage sites.

• Natural host range.

- host range may be related to species but usually not helpful in identifying species. May delineate strains.

• Pathogenicity and cytopathology.

- different inclusion body morphology,

- lack of cross protection,

- seed transmissibility, or lack thereof,

- some aspects of host reaction may be useful (e.g., resistance genes, different responses in key host species).

• Mode of transmission.

- different primary vectors, but vector species not of use in identification to virus species.

• Antigenic properties.

- serological differences.

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