Ecology of Diaporthe eres, the causal agent of hazelnut defects

Abstract

Diaporthe eres has been recently reported as the causal agent of hazelnut defects, with characteristic brown spots on the kernels surface and internal fruit discoloration. Knowledge regarding the ecology of this fungus is poor but, is critical to support a rationale and effective hazelnut crop protection strategy. Therefore, a study was performed to describe and model the effect of different abiotic factors such as temperature (T, 5–35°C, step 5°C) and water activity (aw 0.83–0.99, step 0.03) regimes on D. eres mycelial growth, pycnidial conidiomata development and asexual spore production during a 60-day incubation period. Alpha conidia germination was tested in the same T range and at different relative humidities (RH = 94, 97 and 100%) over 48 h incubation period. Fungal growth was observed from the first visual observation; regarding pycnidia and cirrhi, their development started after 8 and 19 days of incubation, respectively and increased over time. The optimum T for growth was 20–25°C and for pycnidia and cirrhi development was 30°C; aw ≥ 0.98 was optimal for the tested steps of the fungal cycle. The best condition for conidial germination of D. eres was at 25°C with RH = 100%. Quantitative data obtained were fitted using non- linear regression functions (Bete, logistic and polynomial), which provided a very good fit of the biological process (R2 = 0.793–0.987). These functions could be the basis for the development of a predictive model for the infection of D. eres of hazelnuts.

Molecular Phylogenetic Diversity and Biological Characterization of Diaporthe Species Associated with Leaf Spots of Camellia sinensis in Taiwan

“…Our results showed that all species identified in this study reached maximum colony diameter at 25–30 °C and preferred to grow under low acidic to alkaline rather than acidic medium. The observations in the present study are consistent with the results of Arciuolo et al [ 51 ] and Hilário et al [ 12 ]. In the future, these abiotic factors could be used as the basis for developing a predictive model for the infection of Diaporthe taxa of tea plants in Taiwan.…”

“…Only a few studies have shown the effect of environmental factors on the growth of Diaporthe species. The most recent study was carried out by Arciuolo et al [ 51 ], who tested the optimal temperature and water activity required for mycelial growth, pycnidial conidiomata development, and asexual spore production of D. eres , the causal agent of hazelnut defects. Arciuolo et al [ 51 ] concluded that the optimum temperature for mycelial growth of D. eres was observed at 20–25 °C and at 30 °C for pycnidia and cirrhi development.…”

“…The most recent study was carried out by Arciuolo et al [ 51 ], who tested the optimal temperature and water activity required for mycelial growth, pycnidial conidiomata development, and asexual spore production of D. eres , the causal agent of hazelnut defects. Arciuolo et al [ 51 ] concluded that the optimum temperature for mycelial growth of D. eres was observed at 20–25 °C and at 30 °C for pycnidia and cirrhi development. In another study, Hilário et al [ 12 ] observed that four novel pathogens of Diaporthe , namely, D. crousii , D. phillipsii , D. rossmaniae , and D. vacuae , causing twig blight and dieback of Vaccinium corymbosum in Portugal had an optimum temperature for mycelial growth at 20–25 °C.…”

Cytospora and Diaporthe Species Associated With Hazelnut Canker and Dieback in Beijing, China

“…For example, Anisogramma , Anthostoma , Diaporthe , Diaporthella , Diplodia , Dothiorella , and Gnomoniopsis are common fungi that inhabit branches in hazel trees in America, Chile, Italy, and Turkey ( Gottwald and Cameron, 1980 ; Guerrero and Pérez, 2013a ; Linaldeddu et al., 2016 ). Alternaria , Aspergillus , Botryosphaeria , Colletotrichum , Diaporthe , Fusarium , Pestalotiopsis , and Phoma are often isolated from fruits, especially in Turkey and the Caucasus region ( Sezer and Dolar, 2016 ; Battilani et al., 2018 ; Arciuolo et al., 2020 ; Arciuolo et al., 2021 ). Although little information is available, Cytospora corylicola generally occurs in hazelnut growing areas in Europe ( Salerno, 1961 ).…”

Paraconiothyrium fuckelii, Diaporthe eres and Neocosmospora parceramosa causing cane blight of red raspberry in Northern Italy

“…Studies conducted on D. eres in Greece showed that this pathogen has an optimal growth at 25 °C, however, considerable mycelial growth was assessed within the range 20-30 °C (Thomidis and Michailides 2009). Other analyses on water availability and relative humidity confirmed the influence of these abiotic factors on D. eres mycelial growth and conidia germination (Arciuolo et al 2021). Wet and humid conditions have been reported as favourable also for Paraconiothyrium fuckelii development (Martin et al 2017).…”