Molecular characterization of the RNA3 of asparagus virus 2.

Asparagus virus 2 (AV 2) has been detected in all major asparagus growing areas around the world and it has been suggested that, in association with other pathogens, it might be an important factor for the condition called asparagus decline. Although AV 2 was first reported in the 70's, only few of its biochemical characteristics have been actually studied. Some properties of an AV 2 isolate from Guanajuato, Mexico were characterized and its RNA3 cloned and sequenced. Electrophoretic analysis of AV 2 RNA showed 3 genomic RNAs (RNA1. 3.0; RNA2 2.7; and RNA3 2.3 kb) and a fourth, subgenomic, RNA4 of 1.1 kb. In vitro translation data confirmed that coat protein is produced by translation of the subgenomic RNA4, as reported for other bromoviruses. Sequence analysis of AV 2 RNA3 showed two open reading frames identified by sequence comparisons and immunological assays as coding the movement and coat proteins (MP and CP, respectively). AV 2 CP showed a high percentage of identity with the CPs from other members of the subgroup II of the ilarvirus genus. The percentage of identity with other ilarviruses decreased dramatically and in some cases was lower than the values obtained with members of different genera.