Occurrence and genetic variability of partial coat protein gene of Sweet potato leaf curl virus (SPLCV) in Kenya

A survey was conducted to determine the occurrence of sweet potato leaf curl virus (SPLCV) infecting sweet potato in Kenya. Vine cuttings of sweet potato were collected in 2011 from fields in Central, Western and Coastal regions of the country. The cuttings were grown in an insect-proof screen-house and scion grafted to Ipomoea setosa indicator plants. DNA was extracted from leaf samples of graft-inoculated I. serosa and tested for the presence of SPLCV by polymerase chain reaction (PCR) using degenerate and specific primers. The virus was detected in all the regions with incidence rates of 33, 17.0 and 2.6% from Western, Coastal and Central regions, respectively using specific primers. Coat protein gene AV1 from isolates collected from each region was sequenced and their comparison revealed >88.4% nucleotide identity. Phylogenetic grouping using nucleotide and amino acid sequences showed that four Kenyan isolates (Coast3, Central13, Coast15 and Western14) clustered together, while the other remaining five grouped a long with isolates from different parts of the world. The results reveal that Kenyan SPLCV isolates have a clear diversity and are also closely related with other isolates from different parts of the world. The wide distribution of the virus within the country means that urgent measures are needed to clean the farmers planting material to reduce possible losses incurred due to the presence of the virus.    Key words: Sweet potato leaf curl virus, coat protein gene, virus, sweet potato, nucleotide, amino acid.