The Bosco Fontana Nature Reserve, located in the municipality of Marmirolo in the province of Mantova (Italy), represents one of the last plain formations of broad-leaved trees that once covered the Po Valley. The forest is characterized by a high floristic diversity. Among the tree species, the common oak and the white hornbeam dominate, while among the shrubby species, the hazelnut, the black elderberry and the hawthorn stand out. Over the last few years, the presence of symptoms of root rot and sudden death has been observed on several forest species. Since these symptoms are indicative of attacks by oomycetes of the genus Phytophthora, an accurate investigation was conducted in order to isolate and characterize the main species involved in the aetiology of the symptoms observed. To this end, from winter to summer 2024, a network of 34 monitoring plots equidistant 250 meters was set up across the entire forest formation and a further 18 plots were identified at random based on the presence of specific disease symptoms. The incidence of the disease and the mortality rate were calculated using the data collected within 50-meter linear transects set up in different areas of the reserve. A total of 49 samples of roots and rhizosphere and 10 of branches and twigs from 12 plant species were collected at the monitoring plots. In order to intercept the Phytophthora species present along the watercourses of the reserve, traps containing bait leaves were positioned. Laboratory investigations allowed the isolation and genetic identification of 11 species of Phytophthora: P. plurivora (40 isolates), P. honggalleglyana (9), P. acerina (6), P. cactorum (4), P. cinnamomi (4), P. lacustris (4), P. pseudocryptogea (2), P. syringae (2), P. gallica (1), P. gonapodyides (1) and P. psychrophila (1). Furthermore, a new species belonging to clade 9, phylogenetically close to Phytophthora honggalleglyana, was isolated from leaves located along watercourses. From the 10 samples of branches and twigs, 4 species of ascomycetous fungi belonging to the Botryosphaeriaceae family were isolated: Diplodia seriata (6 isolates), Dothiorella iberica (2), Diplodia corticola (1) and Diplodia subglobosa (1). The results obtained highlight a surprising diversity of phytopathogenic species concentrated in a small geographical area, many of which are polyphagous and invasive. Phytophthora plurivora is the most widespread species and directly involved in the decay phenomena affecting the forest formations of the Reserve. Further investigations are necessary to ascertain the introduction routes of these pathogens into the reserve and to evaluate the risks associated with a spread towards the neighbouring agricultural areas.
La Riserva Naturale Bosco Fontana, situata nel comune di Marmirolo in provincia di Mantova, rappresenta una delle ultime formazioni planiziali di latifoglie che un tempo ricoprivano la pianura Padana. Il bosco è caratterizzato da una elevata diversità floristica. Fra le specie arboree dominano la farnia e il carpino bianco mentre tra quelle arbustive spiccano il nocciolo, il sambuco nero e il biancospino. Nel corso degli ultimi anni è stata osservata, su diverse specie forestali, la presenza di sintomi di marciume radicale e morte repentina. Essendo questi sintomi indicativi di attacchi da oomiceti del genere Phytophthora, è stata condotta un'indagine accurata al fine di isolare e caratterizzare le principali specie coinvolte nell'eziologia dei sintomi osservati. A tal fine, tra l’inverno e l’estate 2024 è stato allestito sull’intera formazione boschiva un reticolo di 34 punti di monitoraggio tra loro equidistanti 250 metri ed individuati, at random, ulteriori 18 punti in base alla presenza di sintomi specifici di malattia. L’incidenza della malattia e dell’indice di mortalità sono stati calcolati utilizzando i dati raccolti all’interno di transetti lineari di 50 metri allestiti in diverse aree della Riserva. Nei punti di monitoraggio sono stati raccolti complessivamente 49 campioni di radici e rizosfera e 10 di rami e branche da 12 specie vegetali. Al fine di intercettare le specie di Phytophthora presenti lungo i corsi d’acqua della Riserva sono state posizionate delle trappole contenenti foglie esca. Le indagini di laboratorio hanno consentito di isolare ed identificare su base genetica 11 specie di Phytophthora: P. plurivora (40 isolati), P. honggalleglyana (9), P. acerina (6), P. cactorum (4), P. cinnamomi (4), P. lacustris (4), P. pseudocryptogea (2), P. syringae (2), P. gallica (1), P. gonapodyides (1) e P. psychrophila (1). Inoltre, dalle foglie posizionate lungo i corsi d’acqua è stata isolata una nuova specie appartenente al clade 9 filogeneticamente vicina alla Phytophthora honggalleglyana. Dai 10 campioni di rami e branche sono state isolate 4 specie di funghi ascomiceti appartenenti alla famiglia delle Botryosphaeriaceae: Diplodia seriata (6 isolati), Dothiorella iberica (2), Diplodia corticola (1) e Diplodia subglobosa (1). I risultati ottenuti evidenziano una sorprendente diversità di specie fitopatogene concentrate in una piccola area geografica, molte delle quali polifaghe ed invasive. P. plurivora risulta essere la specie più diffusa e direttamente coinvolta nei fenomeni di deperimento che interessano le formazioni forestali della Riserva. Sono necessarie ulteriori indagini per accertare le vie di introduzione di questi patogeni nella Riserva e per valutare i rischi connessi ad una diffusione verso le aree agrarie limitrofe.
Organismi fitopatogeni coinvolti nei fenomeni di moria e deperimento della componente arborea della Riserva Naturale Bosco della Fontana.
MANTOVANI, LORENZO
2023/2024
Abstract
The Bosco Fontana Nature Reserve, located in the municipality of Marmirolo in the province of Mantova (Italy), represents one of the last plain formations of broad-leaved trees that once covered the Po Valley. The forest is characterized by a high floristic diversity. Among the tree species, the common oak and the white hornbeam dominate, while among the shrubby species, the hazelnut, the black elderberry and the hawthorn stand out. Over the last few years, the presence of symptoms of root rot and sudden death has been observed on several forest species. Since these symptoms are indicative of attacks by oomycetes of the genus Phytophthora, an accurate investigation was conducted in order to isolate and characterize the main species involved in the aetiology of the symptoms observed. To this end, from winter to summer 2024, a network of 34 monitoring plots equidistant 250 meters was set up across the entire forest formation and a further 18 plots were identified at random based on the presence of specific disease symptoms. The incidence of the disease and the mortality rate were calculated using the data collected within 50-meter linear transects set up in different areas of the reserve. A total of 49 samples of roots and rhizosphere and 10 of branches and twigs from 12 plant species were collected at the monitoring plots. In order to intercept the Phytophthora species present along the watercourses of the reserve, traps containing bait leaves were positioned. Laboratory investigations allowed the isolation and genetic identification of 11 species of Phytophthora: P. plurivora (40 isolates), P. honggalleglyana (9), P. acerina (6), P. cactorum (4), P. cinnamomi (4), P. lacustris (4), P. pseudocryptogea (2), P. syringae (2), P. gallica (1), P. gonapodyides (1) and P. psychrophila (1). Furthermore, a new species belonging to clade 9, phylogenetically close to Phytophthora honggalleglyana, was isolated from leaves located along watercourses. From the 10 samples of branches and twigs, 4 species of ascomycetous fungi belonging to the Botryosphaeriaceae family were isolated: Diplodia seriata (6 isolates), Dothiorella iberica (2), Diplodia corticola (1) and Diplodia subglobosa (1). The results obtained highlight a surprising diversity of phytopathogenic species concentrated in a small geographical area, many of which are polyphagous and invasive. Phytophthora plurivora is the most widespread species and directly involved in the decay phenomena affecting the forest formations of the Reserve. Further investigations are necessary to ascertain the introduction routes of these pathogens into the reserve and to evaluate the risks associated with a spread towards the neighbouring agricultural areas.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/80360