Incidence of sweetpotato viruses in Central Luzon, Philippines

Sweetpotao commercial growing areas in Central Luzon particularly Tarlac and Bataan were surveyed for the incidence of sweetpotato viruses. Healthy-looking sweetpotato leaves and those showing symptoms of virus infection were collected and subjected to nitrocellulose membrane-enzyme linked immunoabsorbent serological assay (NCM-ELISA) for the detection of known viruses using the kit and protocol from Centro Internacional de la Papa, Lima Peru. The NCM-ELISA detected sweetpotato feathery mottle virus (SPFMV), sweetpotato mild mottle virus (SPMMV), sweetpotato latent virus (SPLV), sweetpotao chlorotic fleck virus (SPCFV), C-6 virus, sweetpotato mild speckling virus (SPMSV), sweetpotato caulimo-like virus (SPCalV), and sweetpotato chlorotic stunt virus (SPCSV). Six to 8 viruses were found in Tarlac and 3-4 viruses in Bataan. Highest infections were recorded for C-6, SPMSV, SPCalV and SPCSV reaching 100% in almost all areas. Infection of SPFMV ranged from 45-70%. The combination of SPFMV with other viruses was common registering 40-70% complex infection. Mixed infection of 3-6 viruses (SPFMV, SPMMV, SPLV, C-6, SPMSV and SPCalV) was found in Tarlac and 2-4 viruses (SPFMV, C-6, SPMSV and SPCalV) in Bataan. Practically all sweetpotato growing areas of Tarlac are “hotspot” areas of sweetpotato viruses.