"During the productive stage of Corylus avellana (hazelnut) in La Araucanía, Chile (October-December 2018-19), we observed symptoms consisting of a brown-greyish spot occurring at the bottom of the nut and enlarging upwards to the apex, and affecting around 30% of plants. In severe infections the bracts were also affected. Symptoms were consistent with grey necrosis reported in hazelnuts in Italy, and caused by a fungal complex formed mainly by Alternaria spp., Diaporthe spp.and Fusarium spp," the scientists at Universidad de La Frontera (Temuco, Chile) explained.
Causal microorganisms were isolated from infected plants (35 plants, cv. Barcelona), small pieces of kernels and bracts were cut from the margin between diseased and healthy tissues and were observed by variable pressure scanning electron microscopy. Molecular sequencing identified five species: Fusarium sporotrichioides, Alternaria alternata, Diaporthe sp. and its anamorph Phomopsis sp., and Neofusicoccum sp., which were also confirmed by pathogenicity test.
"We noted that Diaporthe sp. showed the highest disease incidence in the early stages. This was in contrast to scientists who found a greater incidence in ripened nuts. This could be attributed to a variation in parameters such as rainfall which may affect dissemination and infection levels of Diaporthe sp., while Alternaria sp. showed the highest disease incidence in the latter stages, which was in accordance with scientists who defined this fungus as a secondary coloniser.
The pathologists continued: To our knowledge, this is the first report of grey necrosis on hazelnuts from Chile and control strategies are urgently required due to high economic losses reported in Europe (i.e. 30% in Italy). In adAdition F. sporotrichioides and A. alternata are highly active mycromycetes and are associated with mycotoxin production which is a human health risk."
Source: Duran P., Barra P.J., de la Luz Mora M., Morina F., Viscardi Sh., Meriño-Gergichevich C., 'First report of fungal complex causing grey necrosis of hazelnut in Chile', 2020, New Disease Reports, 42, 7.