SUMMARYThe particles of a Japanese isolate of apple stem grooving virus (ASGV) contained a single coat protein species with a mol. wt. of 27000 and a single RNA species with a mol. wt. of 2.30 × 106. The corresponding values for particles of a Japanese isolate of apple chlorotic leaf spot virus (ACLSV) were 22000 and 2-48 x 106, respectively. RNAs of both ASGV and ACLSV were plus-sense and polyadenylated. Four virusspecific dsRNA species [mol. wt. ( x 10 -6) 4.8, 4.3, 3-9 and 3.5] were detected in extracts of ASGV-infected plants, whereas three major [mol. wt. ( x 10 -6) 4.9, 4.3 and 3.9] and two minor (4"5 and 3.1) virus-specific dsRNAs were found in ACLSV-infected plants. The biochemical properties of ASGV closely resemble those of potato virus T (PVT) which supports the proposal that ASGV and PVT should be placed in a new virus group.

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