Characteristics of Phomopsis juglandina (Sacc.) Hohn. Associated with Dieback of Walnut in the Climatic Conditions of Southern Romania

Abstract

Phomopsis juglandina (Sacc.) Höhn., which is the conidial state of Diaporthe juglandina (Fuckel) Nitschke, and the main pathogen causing the dieback of branches and twigs of walnut was recently detected in many orchards from Romania. The symptomatological, morphological, ultrastructural, and cultural characteristics, as well as the pathogenicity of an isolate of this lignicolous fungus, were described and illustrated. The optimum periods for infection, under the conditions prevailing in Southern Romania, mainly occur in the spring (April) and autumn months (late September-beginning of October). Strong inverse correlations (p < 0.001) were found between potential evapotranspiration and lesion lengths on walnut branches in 2019. The pathogen forms two types of phialospores: alpha and beta; the role of beta phialospores is not well known in pathogenesis. In Vitro, the optimal growth temperature of mycelial hyphae was in the range of 22–26 °C, and the optimal pH is 4.4–7. This pathogen should be monitored continuously due to its potential for damaging infestations of intensive plantations.

Fungal trunk diseases of fruit trees in Europe: pathogens, spread and future directions

“…Walnut woody parts are commonly invaded by trunk pathogens, including Diatrypaceae, Diaporthaceae, Botryosphaeriaceae and Togniniaceae. In general, the spread of these fungi is similar in regions and countries such as: California (Diaporthe, Neofusicoccum) Agustí-Brisach et al, 2019), Chile (Diaporthe, Diplodia, Neofusicoccum) (Díaz et al, 2018;Luna et al, 2022), China (Botryoshpaeria, Lasiodiplodia, Neofusicoccum) (Yu et al, 2015;Li et al, 2016), the Czech Republic (Cadophora, Cryptovalsa, Diaporthe, Diplodia, Dothiorella, Eutypa, Eutypella, Peroneutypa, Phaeoacremonium) (Eichmeier et al, 2020), Italy (Botryosphaeria, Neofusicoccum) (Gusella et al, 2021), Romania (Diaporthe) (Mihaescu et al, 2020), Spain (Botryosphaeria, Diaporthe, Diplodia, Dothiorella, Neofusicoccum) (López- Moral et al, 2020a;Moral et al, 2010), and Turkey (Botryosphaeria, Neofusicoccum) (Kara et al, 2021;Yildiz et al, 2022). Walnut wood also hosts Ca.…”

Current Insight into Culture-Dependent and Culture-Independent Methods in Discovering Ascomycetous Taxa

“…Some species of Diaporthe (= Phomopsis ) produce different types of conidia, which are known as alpha, beta or gamma [ 36 ]. Mihaescu et al [ 37 ] reported alpha and beta conidia from the pycnidia formed in cultures of Phomopsis juglandina (Sacc.) Hohn.…”