Virus Incidence in Hawaiian Heritage Sweetpotato

In Hawaiʻi, sweetpotato cultivation is important for commercial markets and holds an important role in Indigenous Hawaiian and present-day multicultural food systems. Although Hawaiian heritage cultivars maintained in contemporary botanical collections include ancestral varieties from across the Hawaiian Islands, these have not been systematically evaluated for virus content. Collaborating with a local network, the ʻUala Working Group, we obtained 117 sweetpotato accessions, including Hawaiian heritage cultivars, from the National Tropical Botanical Garden (island of Kauaʻi), Maui Nui Botanical Garden (island of Maui), Waimea Valley and Lyon Arboretum (island of Oʻahu), and Amy Greenwell Ethnobotanical Garden (Hawaiʻi Island). Samples from each cultivar were tested for viral content via reverse transcription PCR for eight sweetpotato viruses: sweetpotato virus G (SPVG), sweetpotato feathery mottle virus (SPFMV), sweetpotato virus 2 (SPV2), sweetpotato virus C (SPVC), sweetpotato leaf curl virus (SPLCV), sweetpotato pakakuy virus (SPPV), sweetpotato symptomless virus 1 (SPSMV-1), and sweetpotato chlorotic stunt virus (SPCSV). Seven of the eight sweetpotato viruses tested for were present, making this the first documented occurrence of these viruses in Hawaiʻi, with the exception of SPVG (documented previously in 2008). High frequencies of the viruses were observed, with results confirming the presence of SPSMV-1 (92%), SPFMV (79%), SPPV (72%), SPVG (65%), SPV2 (44%), and SPLCV (26%), with SPVC showing the lowest frequency of occurrence at 10%. SPCSV was not observed in the sample set. The majority of heritage cultivars exhibited multiple infection combinations with double (11%), triple (23%), quadruple (31%), quintuple (25%), sextuple (4%), and septuple (0.8%) infections observed; less than 2.6% were virus free or hosted a single infection. Here, we report the incidence of sweetpotato viruses and prevalent virus strains in Hawaiian heritage cultivars, which has broad implications for conservation and cultivation of Hawaiian heritage sweetpotato across the Hawaiian Islands.