Evaluation of Sweetpotato Virus Prevalence and Distribution in Support of the Pathogen-Tested Seed Supply System in the Papua New Guinea Highlands

Abstract

In 2020, a survey was conducted across Eastern Highlands (EHP), Jiwaka, and Western Highlands (WHP) Provinces of Papua New Guinea (PNG) to assess sweetpotato (Ipomoea batatas) virus prevalence, virus vectors (aphids and whiteflies), beneficial insects, and wild Ipomoea species as potential virus reservoirs. The study aimed to support the pathogen-tested (PT) sweetpotato seed system by identifying factors associated with virus persistence, transmission, and re-infection. A total of 1,080 sweetpotato samples from 96 gardens were assessed using indicator plants and Nitrocellulose Membrane ELISA (NCM-ELISA). Sweetpotato plants exhibited virus-like symptoms, including leaf curling, vein clearing, distortion, purpling, and chlorosis. EHP recorded the highest disease severity (2.44%), followed by Jiwaka (2.11%), while no visible symptoms were observed in WHP. However, virus indexing detected latent infections, demonstrating the limitations of symptom-based diagnosis. Sweetpotato feathery mottle virus (SPFMV) was the most prevalent virus, followed by Sweetpotato virus G (SPVG), Sweetpotato collusive virus (SPCV), Sweetpotato leaf curl virus (SPLCV), and Sweetpotato chlorotic fleck virus (SPCFV), occurring as single and mixed infections. SPLV was detected as a first record for PNG, increasing the number of documented sweetpotato viruses; however, molecular confirmation is required. Seven wild Ipomoea species were identified as potential alternative hosts, with I. purpurea identified as a potential SPFMV reservoir. Aphid populations remained low (p > 0.05), suggesting limited vector pressure for potyvirus spread, whereas higher whitefly abundance (p < 0.05) indicated potential risk from whitefly-transmitted viruses, particularly Sweetpotato chlorotic stunt virus (SPCSV), the causal agent of sweetpotato virus disease (SPVD) Beneficial insects showed high diversity (H′ = 5.497), richness (S = 274), and evenness (E_H = 0.981), indicating balanced communities supporting natural pest regulation. These findings highlight the importance of virus surveillance, pathogen-tested planting material, and integrated pest and disease management to reduce virus degeneration and sustain sweetpotato production in PNG.