Occurrence of two serotypes of sweet potato chlorotic stunt virus in East Africa and their associated differences in coat protein and HSP70 homologuegene sequences

Amongst samples of the sweet potato chlorotic stunt crinivirus (SPCSV) obta ined from crops of sweet potato in Uganda, two serotypes (S-EA1 and S-EA2) were distinguished using a panel of monoclonal antibodies (Mabs) to a Kenya n isolate of SPCSV. S-EA1 serologically resembled the Kenyan isolate of SPC SV whereas S-EA2 has not previously been reported. S-EA1 was predominant in eastern Uganda whereas S-EA2 was predominant in southern and western Ugand a. S-EA2 tended to occur in more severely diseased sweet potato plants than S-EA1. RNA was extracted from eight plants and replicate clones representi ng the heat shock protein 70 (HSP70) homologue and coat protein (CP) genes were generated by reverse transcription and PCR. Sequence analyses revealed substitutions at two nucleotide positions in the HSP70 homologue gene, alt hough neither affected deduced amino-acid sequences. Nucleotide substitutio ns in the CP gene region, which led to 11 amino-acid substitutions, reveale d two major groupings plus other minor variants. The EMBL accession numbers of the sequences reported in this paper are AJ01 0754 through to AJ01769 (coat protein sequences) and AJ010914 through to AJ 010929 (partial HSP70 homologue gene sequences).