Impact of ‘brown rot’ caused by Gnomoniopsis castanea on chestnut fruits during the post‐harvest process: critical phases and proposed solutions

Abstract

BACKGROUND The brown rot fungus, Gnomoniopsis castanea, is the main organism responsible for the outbreak of chestnut postharvest decay that is threatening the sustainability of the chestnut market in Europe. Currently, no specific strategy is available to mitigate the impact and remediate the high losses of fruits in postharvest storage. In the present study, the different phases of chestnut handling in a standard facility plant were analyzed by evaluating the amount of fruit rot and infection by G. castanea at each phase. RESULTS The warm bath (48 °C) was identified as the critical phase, requiring strict parametrization to effectively inactivate G. castanea in fruits. Laboratory tests indicated that maintaining fruits at 50 °C for a maximum of 45 min provided optimal conditions to completely inactivate G. castanea inoculum during postharvest handling. However, the warm bath at 50 °C and over was not effective in inactivating the complex of fungal taxa responsible for contamination and development of molds. Higher temperatures and extended treatment times caused significant losses in fruit quality, as indicated by taste panel evaluation. Upscaling of postharvest facilities is discussed and critically evaluated. CONCLUSION The warm bath (50 °C for 45 min) is effective in completely inactivating G. castanea in fruits but did not reduce the impacts of the complex of molds responsible for external contamination and mycotoxin production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Gnomoniopsis castaneae: An emerging plant pathogen and global threat to chestnut systems

“…The pathogen is, therefore, considered to be host‐genus specific to Castanea species. G. castaneae is now found on a global scale and has been identified in chestnut tissues throughout Europe (Lewis et al, 2017; Pasche, Calmin, et al, 2016; Visentin et al, 2012), Oceania (Shuttleworth et al, 2012), India (Dar & Rai, 2015), the United States (Sakalidis et al, 2019) and Chile (Morales‐Rodriguez et al, 2021). Although considered specific to Castanea species, G. castaneae has also been identified as a leaf endophyte of manna ash (Oleaceae: Fraxinus ornus ; Ibrahim et al, 2017), in association with cankers of European hazelnut (Betulaceae: Corylus avellana ; Linaldeddu et al, 2016) and common box (Buxaceae: Buxus sempervirens ; Şimşek et al, 2019) and present with unknown activity in holm oak (Fagaceae: Quercus ilex ; Shuttleworth et al, 2012).…”

“…Perhaps the strongest argument against the ACGW as a vector of G. castaneae can be found in their respective ranges. The pathogen has been detected in Australia (Shuttleworth et al, 2012), India (Dar & Rai, 2015), Ireland (O'Loinsigh et al, 2022) and Chile (Morales‐Rodriguez et al, 2021) where there are no documented occurrences of ACGW (EPPO, 2021) and was only recently identified in the United States (Campbell et al, 2019; Sakalidis et al, 2019) where ACGW has had an established and spreading population since the early 1970s (EPPO, 2021; Payne et al, 1983). Thus, the insect cannot or is unlikely to be acting as a vector in these regions, further supporting a different relationship existing between pest and pathogen.…”

First description of adenosine production by Gnomoniopsis smithogilvyi, causal agent of chestnut brown rot

“…This fungus was isolated as the causal agent of an unknown nut rot that began to affect up to 80% of sweet chestnut ( Castanea sativa Mill.) production, depending on location and year, in Europe and Australia (Morales-Rodriguez et al 2022 ). In 2018, Gnomoniopsis smithogilvyi was reported in the Portuguese region of Trás-os-Montes (Coelho and Gouveia 2021 ), which shares a border with Galicia in the Spanish northwest.…”

Trunk Injection Delivery of Biocontrol Strains of Trichoderma spp. Effectively Suppresses Nut Rot by Gnomoniopsis castaneae in Chestnut (Castanea sativa Mill.)

“…Fruit spoilage by diseases, pests and abiotic factors was always one of the main causes of product loss in the chestnut production chain, but normally a low, tolerable percentage of fruits was affected in storage [ 10 ]. This situation changed drastically with the advent of a new fungal disease of the fruit.…”

“…Due to the inconspicuous infections and the endophytic colonization of internal tree and nut tissue by G. castaneae , control measures against this harmful pathogen are, to date, limited and often ineffective [ 15 ]. Currently, most of the control methods rely on water curing, sterilization and the application of chemicals post-harvest [ 10 , 16 ]. However, the efficacy of these methods is strictly linked to disease severity, often being ineffective with high infection levels.…”