Two isolates (A and B) of apple chlorotic leafspot virus (ACLSV) associated with line pattern symptoms in Prunus, glandulosa were isolated in Chenopodium quinoa and purified by a simple method using bentonite clarification, polyethylene glycol precipitation, and caesium sulphate isopycnic centrifugation. Symptoms on herbaceous hosts were as previously reported for ACLSV. No symptoms were observed on a range of ACLSV woody host indicators. Isolates A and B had a coat protein MW of 26 and 24.5 kilodaltons respectively, ssRNA of MW 2.6 x 10⁶ daltons, and dsRNA of MW 5.6 x 10⁶, 4.9 x 10⁶, and 4.5 x 10⁶ daltons. The particle widths were 12 nm and lengths were 782 nm (A) and 732 nm (B). Buoyant density in caesium sulphate was 1.27 g/cc³. In thin sections of C. quinoa, flexuous rods were seen in the cytoplasm and nucleus of young sieve-tube members. Polyclonal antisera prepared against the A and B isolates had high background reactions and required cross-adsorption with host sap. Three monoclonal antibodies (MAB) against isolate A detected Prunus strains while a fourth detected both Malus and Prunus strains in C. quinoa with low background reactions. The broad spectrum MAB could not be used as a trapping antibody but could be directly conjugated with alkaline phosphatase or used in an indirect triple-antibody sandwich ELISA. Tobacco mosaic virus (TMV) recovered from P. glandulosa was identical in serological and physical properties to the TMV-U1 type strain. / Land and Food Systems, Faculty of / Graduate