Detection and Classification of SPLCV Isolates in the U.S. Sweetpotato Germplasm Collection via a Real-Time PCR Assay and Phylogenetic Analysis

Abstract The United States Department of Agriculture–Agricultural Research Service sweetpotato (Ipomoea batatas) germplasm collection contains accessions that were initially collected from various countries worldwide. These materials have been maintained and distributed as in vitro plantlets since the mid-1980s. The status of viral infection by the emerging Sweet potato leaf curl virus (SPLCV) and other Begomovirus spp. in this germplasm has yet to be determined. In order to minimize the potential distribution of virus-infected clones, all accessions in the collection were tested for SPLCV using a real-time polymerase chain reaction assay. In total, 47 of 701 accessions of in vitro plantlets tested positive for SPLCV. The presence of SPLCV detected in these materials was confirmed via biological indexing using the indicator plants I. nil and I. muricata. Symptoms appeared more rapidly on I. muricata than on I. nil. Nucleotide polymorphisms among the isolates were evaluated by sequencing the AV1 coat prote...