DNA sequencing was carried out using 4 pmol of a specific primer and 0.1 mg of a cDNA clone. The sequence reaction was incubated at 378C for 10 min and then analysed via a manual sequencing gel system. RNA sequencing was carried out under the same conditions as the DNA sequencing except that 10 mg of the total plant RNAs, 2 mg of the virion RNAs or 1 mg of a single RNA were used as a template and that the sequence reaction was incubated at 428C for 30 min.