VIEW ARTICLE

Etiology

Physical and Chemical Properties of the Particles and Ribonucleic Acid of Blueberry Leaf Mottle Virus. D. C. Ramsdell, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; R. Stace-Smith, Agriculture Canada, Research Station, Vancouver, B.C. V6T 1X2, Canada. Phytopathology 71:468-472. Accepted for publication 15 October 1980. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/Phyto-71-468.

The properties of blueberry leaf mottle virus (BBLMV), a serologically closely related isolate from grapevine in New York state (NY isolate), and the serologically distantly related grapevine Bulgarian latent virus (GBLV) from Europe were compared. Of these three isolates, only BBLMV infected highbush blueberry (cultivar Rubel) seedlings that were inoculated with purified virus. In linear-log sucrose density gradients, the middle (M) and bottom (B) components of both BBLMV and GBLV had estimated sedimentation coefficients of 120 S and 128 S, respectively. The M and B components of the NY isolate were not resolved and produced a shouldered peak that sedimented between 120 and 128 S. The proportion of M to B component was greater for BBLMV preparations while the converse was true for GBLV. When the M and B components of BBLMV were separated by sucrose density gradient centrifugation and inoculated separately to Chenopodium quinoa, they were one seventh as infectious as when the M and B inoculum components were used in combination. Combined M and B components of BBLMV had E_max = 260 nm, E_min = 240 nm, and E_260/280 = 1.69; top component (T) had E_260/280 = 0.94. Centrifugation of M and B components of BBLMV to near equilibrium in CsCl revealed a larger M-component peak and a smaller B-component peak at buoyant densities of 1.471 and 1.497 g/cm³, respectively. GBLV was resolved into a sharp M-component peak which was twice as large as the sharp B-component peak, with buoyant densities of 1.475 and 1.492 g/cm³, respectively. The CsCl gradient profile of the NY isolate was similar to that of BBLMV, but the peaks were broader and had buoyant densities of 1.470 and 1.488 g/cm³, respectively. The molecular weight of the coat protein subunit for all three virus isolates was 54,000 in 5% SDS polyacrylamide gels. The nucleic acid of BBLMV was degraded by RNase, but not by DNase. The RNA was single stranded and exhibited a T_M = 60 C and 15.4% hyperchromicity when melted over a temperature range of 30–99 C. The RNA-1 and RNA-2 of all three virus isolates was resolved in 2.4% polyacrylamide gels, and had molecular weights of 2.35 and 2.15 × 10⁶, respectively. Blueberry leaf mottle virus is distinct from its serologically distant relative, GBLV, and we propose that BBLMV be included as an independent member of the nepovirus group. The NY isolate is so closely related to BBLMV that it should be considered a closely related strain of BBLMV.