Symptoms and disease virulence assessment in commercial pepper cultivars caused by Pepper chat fruit viroid

Abstract

The symptoms caused by viroids differ, ranging from asymptomatic to mild-or-severe symptoms. Pepper plant symptoms caused by the Pepper chat fruit viroid (PCFVd) are mild compared to those affecting tomato plants; however, there is not much more known of the symptomatology on pepper plants. Symptoms that could be used for disease virulence assessment in pepper plants were elucidated from 31 commercial pepper cultivars belonging to Capsicum annuum and C. frutescens that had been purchased from agricultural shops. The plants were mechanically sap-inoculated at the seedling growth stage and observed weekly for symptom development, with disease virulence evaluations performed at 4, 8, and 12 weeks post inoculation. Infection of all plants was verified based on reverse transcription-polymerase chain reaction, along with visual evidence of growth reduction, including leaf rugosity and leaf size reduction, a narrow canopy of the blocky and elongated fruit shapes for C. annuum and explicit apical stunting with small apical leaves of the elongated fruit type for C. frutescens. The disease virulence assessment was designed based on these symptoms to produce a score with 0–10 disease virulence levels (DVLs). The results showed that the pepper cultivars displayed responses to PCFVd with DVL scores of 1.00–8.00, with no PCFVd transmission being recorded from seeds to seedlings for the 3 test cultivars. This finding indicated that the genetic resources of pepper cultivars against PCFVd were as low as 1.00 DVL. However, the low DVL pepper cultivars could provide an inoculum source to other susceptible plants via mechanical transmission.