Isolation, Identification, and Polymerase Chain Reaction Analysis of Pathogenic Fungi in Sweet Orange (Citrus sinensis L.) Fruits during Storage

Pathogenic fungi play an important role in the shelf life of stored produce. Fruits of ‘Valencia’, ‘Ibadan Sweet’, and 'Washington Naval' sweet orange fruits showing symptoms of spoilage at storage were collected and used for the pathogenicity test. For fungal identification, the cultural and morphological features and the PCR of the isolates were examined. Five healthy fruits of each of the three varieties at physiological maturity were inoculated with the test fungi, replicated three times, and arranged in complete randomized design. The control fruits were inoculated with only sterile potato dextrose agar. The fungi identified were Aspergillus niger, A. avus, Penicillium citrinium, and Rhizomucor pusillus. The pathogenicity results demonstrated a higher incidence and decay severity of A. niger. The PCR-DGGE analysis confirmed that spoilage of fruits was attributed to A. spp. and P. spp. earlier reported by microscopic analysis in this study. In general, a significant difference at P ≤ 0.05 was found between the inoculated fruits and the control. It is concluded that the pathogenicity test and molecular PCR-DGGE analysis could be complementary methods in the confirmation of microscopic identification of isolated fungi.