Preliminary studies on Phomopsis castanea and other organisms associated with healthy and rotted chestnut fruit in storage

Abstract

The microflora of chestnuts during storage, and the effect of post-harvest treatments on storage rots, were investigated over two years. Isolations from apparently healthy chestnuts stored for up to 152 days at 0°C showed that nuts were colonised by a range of microorganisms. The organisms isolated most often from shell or kernel tissue were Phomopsis, Botrytis, yeasts, Penicillium, Ceuthospora, bacteria, Cladosporium, Altemaria, Truncatella, Epicoccum and Phoma. Phomopsis castanea was the fungus which was most frequently isolated from apparently healthy nuts. Results suggest that this fungus can grow from the shell into the kernel during storage. Large variations were observed in the type and frequency of microorganisms isolated from nuts between the two years. A storage trial over 172 days during the second year showed that controlled atmosphere storage combined with an initial 6% carbon monoxide atmosphere significantly reduced the incidence of rot from 15.3% in air-stored nuts to 6.1%. A dry heat treatment before storage damaged nuts, resulting in high rot levels (55.3%). The fungi most commonly isolated from the rotted nuts comprised Penicillium spp., Botrytis cinerea, Phomopsis castanea, Fusarium spp., Truncatella sp., Mucor sp. and Cytospora sp.. This is the first record of these fungi associated with rotting of chestnuts in Australia.