Vegetative incompatibility and potential involvement of a mycovirus in the Italian population of Geosmithia morbida

Studies carried out during an Italian outbreak of the Thousand Cankers Disease of walnut, demonstrated that non-coalescing cankers on host plants, separated by equidistant uninfected zones, were associated with incompatible strains of Geosmithia morbida. Confirmation of the vegetative incompatibility of paired fungal isolates, randomly collected from black walnuts, was obtained from observations of a clear separation zones and the absence of anastomoses. Pairing tests with two incompatible monoconidial strains indicated differences in morphology and growth rates. Electron microscopy revealed the presence of icosahedral mycovirus-like particles in one of the monoconidial strains that demonstrated low degrees of virulence in planta compared with a particlefree monoconidial strain. The occurrence of a vegetative incompatibility system in recently introduced populations of G. morbida has considerable implications for fungal biology. Incompatibility in G. morbida and potential direct or indirect roles of the observed virus-like particles have potential ecological and epidemiological consequences. \ua9 Firenze University Press

Evaluating the impact of Hymenoscyphus fraxineus in Trentino (Alps, Northern Italy): first investigations

The spread of Hymenoscyphus fraxineus has been causing great concern regarding the survival of European ash (Fraxinus excelsior) throughout Europe since the 1990s. The disease was first recorded in Trentino (southern Alps, Italy) in 2012 and has spread throughout the mountain landscape, where ash trees are scattered in small and isolated stands in different valleys. The status of the disease was checked by monitoring the damage to natural regeneration and adult trees in 90 sites spread over the whole region. The survey confirmed the complete colonization by the pathogen of the whole investigated area, with high levels of damage to both young and adult ash trees. Regeneration (both seedlings and saplings) was observed to be affected by the fungus in 88 plots out of 90. Out of 4486 examined young European ashes, 2261 (50.4%) were affected and 789 (17.6%) were already dead. Ten of the 384 assayed flowering ashes (Fraxinus ornus) showed symptoms on branches and apical stems, similar to those observed for European ash. Isolation and molecular analysis proved the presence of the fungus on both symptomatic European and flowering ashes. The examined 386 adult trees showed different levels of damage, sometimes reaching more than 75% of the crown. Some individual trees (42) growing close to severely damaged trees appeared fully healthy, which suggests the possible existence of some resistant/tolerant individuals in the examined populations

Changes in ectomycorrhizal diversity in a declining Quercus ilex coastal forest

Oak decline is generally accepted to be the result of a dynamic interaction between oaks and a mix of abiotic and biotic causes, within which environmental stresses (drought, salinity, frost, low fertility) may be important as predisposing factors. As a result of these interactions, trees gradually begin to show symptoms of general suffering, which below ground consist of functional and anatomical modifications to the rootlets and changes in the ectomycorrhizal status. The present study was performed in a coastal Quercus ilex forest, where decline symptoms appeared after heavy land reclamation in the adjoining areas, which caused a rapid lowering of the ground water level and the underground intrusion of seawater from the neighbouring Adriatic Sea into the forest itself. A forest survey including examination of rootlet features from asymptomatic and declining trees suggested that drought and salinity were involved in this decline. The relative frequency of the most recurrent ectomycorrhizal morphotypes distinguished clearly between asymptomatic, weakly declining and strongly declining trees, suggesting that the occurrence and distribution of only a limited number of morphotypes can give an indication of the severity of the decline. Moreover, of all the morphotypes observed only one third were found in all three decline classes, while the remaining two thirds were gradually replaced by others as the proportion of declining trees increased, where the number of morphotypes was greater. The hypothesis of an adaptive response of the ectomycorrhizal community to decline or to the predisposing factors of decline is discussed

Vegetative incompatibility and potential involvement of a mycovirus in the Italian population of Geosmithia morbida

Studies carried out during an Italian outbreak of the Thousand Cankers Disease of walnut, demonstrated that non-coalescing cankers on host plants, separated by equidistant uninfected zones, were associated with incompatible strains of Geosmithia morbida. Confirmation of the vegetative incompatibility of paired fungal isolates, randomly collected from black walnuts, was obtained from observations of a clear separation zones and the absence of anastomoses. Pairing tests with two incompatible monoconidial strains indicated differences in morphology and growth rates. Electron microscopy revealed the presence of icosahedral mycovirus-like particles in one of the monoconidial strains that demonstrated low degrees of virulence in planta compared with a particle-free monoconidial strain. The occurrence of a vegetative incompatibility system in recently introduced populations of G. morbida has considerable implications for fungal biology. Incompatibility in G. morbida and potential direct or indirect roles of the observed virus-like particles have potential ecological and epidemiological consequences

Ultrastructural modifications in Common ash tissues colonised by Chalara fraxinea

Chalara fraxinea, the cause of ash dieback, is present in many European countries and constitutes a severe threat to Fraxinus spp. in forests, urban areas and nurseries. This study investigated tissue colonisation strategies of the parasite in Common ash at ultrastructural level and demonstrated that C. fraxinea develops intracellularly, moving through the cells and easily colonising the phloem, paratracheal parenchyma and parenchymatic rays. However, damage to either the plasmalemma or cell walls was not observed under our experimental conditions. Furthermore, the presence of intrahyphal hyphae was frequently detected, which are likely associated with a regeneration mechanism

The potential for pesticide trunk injections for control of thousand cankers disease of walnut

Thousand cankers disease, caused by the pathogen Geosmithia morbida vectored by the bark beetle Pityophthorus juglandis, has emerged as an important disease of walnut trees in Europe. The present study was performed to evaluate the efficacy of trunk injections of four commercial fungicides and one insecticide for control of the fungus and its vector. Laboratory tests indicated that fungicides containing prochloraz + tetraconazole were the most effective. Field trials on non-infected trees allowed for the selection of a mixture containing prochloraz and tetraconazole (Binal Pro), the insecticide abamectin (Vertimec EC) and the adjuvant 2-(2-ethoxyethoxy) ethanol (CarbitolTM) as having rapid host uptake. Injections of this formulation in naturally infected black walnut trees reduced the presence of G. morbida, supporting trunk injection as an efficient and low impact technique to manage fungal damage on infected trees

First report of Neofusicoccum parvum and Phytophthora palmivora causing fruit rot of pomegranate in Italy

Severe pomegranate yield losses due to fruit diseases have recently been observed in several orchards in Veneto (north-eastern Italy). Given the economic relevance of these emerging diseases, an in-depth study was conducted in ten orchards distributed in the main producing areas in order to investigate the aetiology. From autumn 2020 to autumn 2023, eighty-two symptomatic fruits were sampled to isolate the causal agents. Based on morphology, colony appearance and DNA sequence data, seventy-seven isolates were obtained and identified. These included Coniella granati (Fam. Schizoparmaceae, 39 isolates), Neofusicoccum parvum (Fam. Botryosphaeriaceae, 29) and Phytophthora palmivora (Fam. Peronosporaceae, 9). Pathogenicity trials conducted on ripe pomegranate fruits confirmed the aggressiveness of the three species. Results obtained have allowed us to expand knowledge on emerging pomegranate pathogens. Neofusicoccum parvum and P. palmivora are reported here for the first time as fruit rot agents on pomegranate in Italy

51\ub0 Corso di Cultura in Ecologia. Ecologia del suolo e futuro, mantenendo i piedi per terra - Soil ecology and future, keeping our feet on the ground

L\u2019obiettivo principale degli 11 interventi e\u300 quello di evidenziare i meccanismi di funzionamento del suolo considerando l\u2019interazione di tutte le sue componenti. Lo scopo finale e\u300 quello di insegnare a gestire la risorsa suolo di un territorio in modo saggio e consapevole, basandosi su risultati di ricerche scientifiche e di ambito biologico