First report of Peroneutypa scoparia associated with canker disease on Ficus carica in northern Iran

Edible fig (Ficus carica) has a high commercial value in Iran, one of the world's major fig producers. Fig cankers represent a constant and significant challenge to plantations in Iran (Mostowfizadeh-Ghalamfarsa et al., 2022). Symptoms include lesions on the trunk and branches, death of bark and woody tissues, limb dieback, leaf yellowing, defoliation and consequently, death of the fig trees (Figure 1). In December 2020, a field survey was performed to investigate the diversity and pathogenicity of ascomycete fungi associated with canker and dieback symptoms on fig trees in Mazandaran province, northern Iran (Bolboli et al., 2022a; Bolboli et al., 2022b). As part of this survey, two unknown isolates were recovered from one fig tree. When the isolates were grown on potato dextrose agar (PDA) at 25°C, the mycelium was white and cottony at first, then grey to brown. Conidia were filiform, unicellular and hyaline, and infrequently observed. The β-tubulin gene of both isolates was amplified and sequenced with the primers T1/BT2b (He et al., 2022) and analysed phylogenetically using Maximum Likelihood (ML) and Bayesian inference (BI) methods. Based on our results both isolates were identical and belonged to the Diatrypaceae family (Figure 2). They were included in a distinct monophyletic clade corresponding to Peroneutypa scoparia (syn. Eutypella scoparia) with strong support values (ML/BI = 100/1) (Table 1, Figure 3). The pathogenicity of the two isolates was evaluated in the winter by inoculation of two one-year-old fig saplings (cvs. Sabz and Siah) and detached shoots of other economically important trees using a 6-mm diameter PDA disc colonised with the isolate's mycelium. Non-colonised PDA plugs were used for the negative controls. Twenty-one days after inoculation in a greenhouse at 25±3°C (day) and 18±3°C (night), the lesion lengths were measured and analysed using one-way ANOVA with the Tukey HSD test (P < 0.05) to compare differences in the mean values. For re-isolations from artificially inoculated stems and saplings, five pieces (2 × 5 mm) of necrotic tissue from the edge of each lesion were cut, surface-disinfected, and placed on PDA. Peroneutypa scoparia was re-isolated from all the lesions fulfilling Koch's postulates. The artificial inoculations of one-year-old cultivars of fig saplings led to disease symptoms including wood discolouration and necrosis on the stems, and leaf yellowing in both fig cultivars (Figure 4). Peroneutypa scoparia was also pathogenic to other economically important horticultural trees, including almond, apple, apricot, blackberry, cherry, grapevine, loquat, mulberry, pistachio, persimmon, pomegranate, oak, olive, quince and walnut, based on a host range evaluation on detached shoots. The mean lesion lengths of the inoculated trees were significantly different compared with each other at P < 0.05 (Figure 5, Table 2). Peroneutypa scoparia is associated with canker, stem blight and dieback symptoms on blueberry in northern Italy (Guarnaccia et al., 2020) and on grapevine in California (Úrbez-Torres et al., 2020). Closely related taxa such as Eutypella species (e.g., E. citricola and E. microtheca) also cause canker and branch dieback with gummosis on Prunus spp. and grapevine in California (Moyo et al., 2018; Úrbez-Torres et al., 2020). To our knowledge, this is the first report of P. scoparia on edible fig in both Iran and globally. This species most likely has a wider host range than fig and other reported hosts. This disease could represent a potential threat to fig industries in Iran and other fig-growing countries and may have phytosanitary implications for the international trade of plants. This work was supported by Iran National Science Foundation (INSF), grant number 97010489.