- C L Johnston, R Jacobs and L Korsten
- Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria 0002, South Africa
- 2006
Penicillium species can cause major losses to the fruit export industry, as post-harvest decay of litchi fruit by this genus dramatically reduces the shelf life of the fruit. This study was aimed at identifying the most dominant Penicillium species throughout the litchi export chain and drawing comparisons between local and international isolates. From this study, several critical control points affecting cross-contamination of litchi fruit during export were identified. Morphological, as well as molecular methods such as PCR-RFLP were used in the identification of these Penicillium species. Thirteen of the most dominant Penicillium species isolated during the 2004/05 season were identified as P. expansum, P. griseofulvum, P spinulosum, P. brevicompactum, P corylophilum, P verrucosum, P aurantiogriseum, P sclerotiorum, P glabrum, P solitum, P citrinum, P chrysogenum and P crustosum. Penicillium expansum was the most dominant species isolated in this study. Penicillium citrinum was only isolated locally, which may indicate that this species does not affect the quality and safety of the fruit during export. These 15 groups were divided into four molecular-based groups, through PCR-RFLP. Future research will involve the investigation of alternative gene regions, which may identify appropriate restriction enzymes to differentiate between these Penicillium species.
Summary:
The study aimed to identify the dominant Penicillium species throughout the litchi export chain and compare local South African and international isolates.
Penicillium species cause major post-harvest decay in litchi, reducing fruit shelf life and causing economic losses.
Thirteen dominant Penicillium species were identified during the 2004/05 season, including P. expansum (most dominant), P. griseofulvum, P. spinulosum, P. brevicompactum, P. corylophilum, P. verrucosum, P. aurantiogriseum, P. sclerotiorum, P. glabrum, P. solitum, P. citrinum, P. chrysogenum, and P. crustosum.
Penicillium citrinum was found only locally and not in international samples, indicating it may not impact exported fruit quality.
Samples were collected from several points in the export chain, including local packhouses and international repacking/distribution centers in Europe.
Molecular methods (PCR-RFLP) and morphological techniques were used to identify species and group them into four molecular clusters.
The study found that South African packhouses pose relatively less risk of introducing Penicillium species compared to international stages, with most isolates originating from Antwerp, Belgium.
Some species like P. verrucosum and P. expansum can produce mycotoxins (ochratoxin A and patulin) posing human health risks.
The ITS gene region used for molecular identification was highly conserved, making differentiation between all species challenging with the tested restriction enzymes.
The study recommends further research on alternative gene regions and restriction enzymes to improve molecular differentiation.
Identification of critical control points for cross-contamination during handling and export can help minimize decay and improve litchi fruit safety and shelf life.