Integrative Molecular and Pathogenic Characterisation of Penicillium oxalicum Driving Postharvest Loss and Quality Decline in Papaya (Carica papaya L. cv. Pusa Dwarf)

Abstract

Postharvest decay of papaya (Carica papaya L.) substantially affects fruit shelf life and quality under tropical conditions. This study aimed to isolate, identify and molecularly characterise the fungal pathogen associated with postharvest decay of 'Pusa Dwarf' papaya in Eastern Bihar and to assess its effects on fruit quality. The pathogen was isolated on PRDA and identified morphologically as Penicillium sp. Molecular identification through ITS rDNA sequencing (approximately 550 bp) supported provisional identification as P. oxalicum. Pathogenicity assays showed that lesion development was greater in injured fruit (28.4 mm on day 10) than in uninjured fruit (19.2 mm), and sporulation was also higher in injured fruit (72.6 × 10⁵ spores/mL). Infected fruits showed weight loss of up to 96.8% after 30 days of storage at 25 °C. By day 30, infected fruits contained 18.6 mg/100 g ascorbic acid, 2.3 °Brix total soluble solids and 0.21% titratable acidity, compared with 44.2 mg/100 g, 4.5 °Brix and 0.42%, respectively, in healthy fruits. These findings indicate that the isolate associated with postharvest papaya rot can cause substantial quantitative and qualitative deterioration and support the need for improved postharvest management.