Papaya ringspot virus type P affects photochemical efficiency (JIP test parameters) in young papaya plants

Papaya ringspot virus type P (PRSV-P) is the causal agent of one of the most devastating viral diseases affecting papaya crops, with symptoms including mosaic and chlorosis. Although understanding of the photochemical changes in infected plants is limited, research such as the present study aims to bridge this gap by investigating how PRSV-P affects the physiological aspects of papaya plants. In this study, chlorophyll fluorescence variables, measured by the JIP test, are used to analyze these changes in ten papaya accessions. The fluorescence variables were measured five days before and 7, 16, 30 and 64 days after inoculation (DAI). Nine of the ten accessions studied showed severe symptoms of the disease and high percentage disease indices (PDIs). These accessions exhibited significant changes in photochemical variables at 30 DAI, including declines in initial and maximum fluorescence and phenomenological fluxes. In addition, relative variable fluorescence in stage I (V_I) increased from 16 DAI onwards. Changes in these variables indicate damage to photosynthetic pigments and the electron transport chain, and inactivation of PSII reaction centers. By contrast, papaya accession BAG89 exhibited resistance to PRSV-P, with a symptom incubation period of 56 days and PDI of only 1.67 %. This accession maintained more stable photochemical efficiency under viral infection. These findings help understand the photochemical response of papaya to viral infection and highlight the potential of BAG89 as a genetic resource in developing resistant varieties, contributing to sustainable management of this virus in cultivation areas.