Pg. 24-32 Fungal postharvest pathogens of litchi fruit in South Africa

Filamentous fungi associated with postharvest decay of litchi fruit were investigated in South Africa. Filamentous fungi were identified and quantified with specific reference to geographical region and cultivar. The variability between cultivars was more prominent for individual fungal populations, than for the total fungal community. Highly variable fungal diversities were reported on fruit sourced from different geographical regions. A total of 25 different filamentous fungal genera (48 species) were isolated from perishing fruit. The predominant filamentous fungal genus isolated at all times was Phomopsis sp., accounting for 21.3% of all isolates. The pathogenicity of 12 fungal genera was confirmed on cv. Madrass litchi fruit. This study demonstrated that the most prevalent postharvest pathogens of litchi fruit in South Africa are Phomopsis sp., Pestalotiopsis guipinii, Trichoderma harzianum, Alternaria alternata, Lasiodiplodia theobromae and Dothiorella sp. Less prevalent pathogens are Fusarium oxysporum, Colletotrichum gloeosporioides, Rhizopus stolonifer, Penicillium expansum, Phoma spp. and Aspergillus niger. Non-pathogenic fungi found to readily colonise decaying litchi fruit included Cladosporium spp., Nigrospora spp., Gliocladium roseum, Periconia cookei, Acremonium sp. and Penicillium species.

Summary:

• The study investigated filamentous fungi associated with postharvest decay of litchi (Litchi chinensis Sonn.) fruit in South Africa, focusing on the effects of cultivar and geographical region.
• A total of 25 different filamentous fungal genera and 48 species were isolated from decaying litchi fruit collected from three production regions: Tzaneen, Hazyview, and Nelspruit.
• The most predominant fungal genus isolated throughout the study was Phomopsis sp., accounting for 21.3% of all isolates.
• The species diversity of fungi differed between the two main commercial cultivars studied: Mauritius and Madrass, with some fungi more prevalent on one cultivar than the other.
• Geographical location also influenced fungal communities; for instance, Hazyview had the lowest fungal species diversity.
• Pathogenicity tests confirmed 12 filamentous fungal genera as postharvest pathogens on the cultivar Madrass.
• The most prevalent postharvest fungal pathogens identified were Phomopsis sp., Pestalotiopsis guipinii, Trichoderma harzianum, Alternaria alternata, Lasiodiplodia theobromae, and Dothiorella sp.
• Less prevalent pathogens included Fusarium oxysporum, Colletotrichum gloeosporioides, Rhizopus stolonifer, Penicillium expansum, Phoma spp., and Aspergillus niger.
• Non-pathogenic fungi frequently colonizing decaying litchi fruit included Cladosporium spp., Nigrospora spp., Gliocladium roseum, Periconia cookei, Acremonium sp., and Penicillium species.
• The study emphasized that pre-harvest climatic conditions and inoculum load impact the postharvest fungal composition and disease expression.
• Results highlighted the uniqueness and complexity of the South African postharvest litchi disease complex and the influence of cultivar and region on fungal populations.
• The findings help in understanding fungal diversity to inform improved management of postharvest diseases in litchi fruit for improved marketability during storage and export.