Date of this Version
Acta Horticulturae 431, 1996 - Tospoviruses and Thrips.
A procedure for the purification of peanut bud necrosis virus (PBNV) nucleocapsids was developed. Virus particles were treated with nonionic detergent to disrupt the envelope membrane and free nucleocapsids were separated. into three lightscattering zones after sucrose gradient centrifogation. Nucleocapsids from the top zone contained S RNA and traces ofM RNA; whereas, nucleoplasids from the middle zone contained M RNA with detectable levels of S RNA and those from the bottom zone contained L RNA with traces of M and S RNAs. Clones from a cDNA library made from the purified PBNV Sand M RNAs were characterized and sequenced. Comparison of the amino-acid sequence of the nucleocapsid (N) protein (276 amino acids) encoded by the S RNA with corresponding sequences from other tospoviruses indicated that PBNV was closely related to members of serogroup IV, i.e., watermelon silver mottle virus (WSMV) and tomato isolate of PBNV (PBNV-To) (identity and Similarity values were 86% and 94%, respectively). A more distant relationship was evident between PBNV and members ofserogroups L II, and III (the N protein showed 30-34% identity and 51-53% similarity). Sequence comparisons of the PBNV glycoprotein precursor (GP) protein (1121 amino acids, encoded by the M RNA), also showed distant relationship between PBNV and tomato spotted wilt virus (TSWV) (serogroup I) and impatiens necrotic spot virus (INSV) (serogroup III) (37% identity and 58-59% similarity). These findings suggest that PBNV is a distinct species in serogroup IV.