Effect of Papaya Ring Spot Virus Infection the Fruit Quality of a Tolerant Papaya Variety, ‘Red Lady’

Abstract

attachedCarica papaya L. ‘Red Lady’, a papaya ring spot virus (PRSV), tolerant variety was introduced to Sri Lanka in early 2000. However, recently, plants with severe symptoms of PRSV were observed in the fields while fruits in local markets were seen with abundant ring-spot symptoms. As the virus is known to have no considerable effect on the yield of tolerant varieties, this investigation was focused on verifying the effect of PRSV on the quality of “Red Lady” fruits. Since the initial screening showed that plants with no virus symptoms also carry PRSV, they were categorized into mild and severe disease levels based on the results of “DAS-ELISA” test. Severe PRSV infections significantly decreased the contents of total soluble solids (TSS), total amino acids, methionine, tryptophan, sodium and flesh brightness. Furthermore, contents of β-carotene, ascorbic acid, crude proteins and certain minerals (K, Mg, Ca, Fe, Zn) were also affected but no marked effect was observed on titratable acidity, pH, flesh firmness and lycopene contents between two disease levels. PRSV infection of ‘Red Lady’ papaya considerably reduces the fruit nutritional quality with respect to its total free amino acids, methionine, tryptophan and Na contents and postharvest parameters such as TSS and flesh brightness.