Armillaria is a white-rot basidiomycete affecting both timber and agronomic trees, which causes significant economic damages worldwide. In Europe five Armillaria species are known, but only two of them are particularly dangerous (A. mellea and A. ostoyae). Because of climate changes and recent forestry maintenance practices, the trees stress enhances the virulence and the spread of the pathogen. At present there aren’t effective means of control against Armillaria; it is only possible to prevent the disease or to treat it at early stages. There aren’t distinguishable symptoms, an early diagnosis is thus difficult to obtain. In addition, it is not easy to identify Armillaria at the species level, since identification with both morphologically methods and incompatibility tests (somatic and sexual) requires some months and often gives ambiguous results. It is therefore of primary importance the investigation of alternative methods to identify Armillaria. The present study concerns the Trentino Alto Adige region; 80 Armillaria basidiocarp samples were identified at the species level with molecular methods. The aim was to compare the identification effectiveness of two different sequences (ITS 1 and 4 and Elongation Factor-1 α). The identification with the EF-1 α gene sequence resulted in a higher precision and reliability compared with the one obtained with ITS gene sequence. This result is consistent with the phylogenetic trees built with the respective sequences. The distribution of the Armillaria species in Trentino Alto Adige was highlighted and a comparison with other previous studies was made. A. borealis (typical of cold environments) resulted as the most frequent species (25%) and it was found in the Bolzano province (high altitude habitats); A. gallica, A. cepistipes and A. ostoyae (22%, 21%, 19%) are following and at last A. mellea (10%) was found. No sample of A. tabescens (termophilic species typical of Mediterranean climate) was reported. It was possible to observe, both from the phylogenetic trees and from the specific primers results, that A. borealis splits into two different clusters. This could indicate that further investigations about this species phylogeny are requested. In conclusion the present study confirmed the superior effectiveness of the identification method based on EF-1 α sequence; furthermore, it allowed a more complete knowledge about the distribution of Armillaria species in Trentino Alto Adige region, since previous studies concerned more limited areas and specific habitats.
Armillaria è un basidiomicete agente di carie bianca su piante forestali, da legno e da frutto, che causa in tutto il mondo ingenti danni economici. In Europa sono riconosciute cinque specie di Armillaria, di cui solo due sono particolarmente pericolose (A. mellea e A. ostoyae). Con i cambiamenti climatici e le più recenti pratiche di manutenzione forestale, lo stress subito dagli alberi favorisce ed aumenta la virulenza e la diffusione del patogeno. Al momento non esistono metodi di controllo efficaci contro Armillaria; è soltanto possibile prevenire la malattia o intervenire ai primi stadi dell'infezione. Tuttavia, non essendoci sintomi distintivi, la diagnosi precoce è difficile. Inoltre, poiché i tempi richiesti per l’identificazione morfologica o di incompatibilità (somatica e sessuale) richiedono mesi e spesso danno risultati ambigui, è complicato identificare Armillaria a livello di specie. È dunque di grande importanza la ricerca di metodi alternativi per l’identificazione di Armillaria. Questo studio ha interessato la regione del Trentino Alto Adige; sono stati identificati con metodi molecolari, a livello di specie, 80 campioni di Armillaria allo scopo di confrontare l’efficienza di identificazione di due diverse sequenze nucleotidiche (ITS 1 e 4 e l’Elongation Factor-1 α); L’identificazione con le sequenze del gene EF-1 α è risultata molto più precisa ed affidabile rispetto a quella ottenuta con le sequenze ITS, come confermato dagli alberi filogenetici costruiti con le rispettive sequenze. È stata messa in luce la distribuzione delle specie di Armillaria in Trentino Alto Adige, confrontando i risultati ottenuti con quelli di studi precedenti. La specie più frequente (25%) è risultata A. borealis (tipica di climi freddi), riscontrata nella provincia di Bolzano (habitat di alta quota); seguono A. gallica, A. cepistipes e A. ostoyae (22%, 21%, 19%) ed in ultimo A. mellea (10%). È risultata assente A. tabescens, specie termofila tipica del clima mediterraneo. Dagli alberi filogenetici e dai risultati dei primer specifici è stato possibile osservare che A. borealis si suddivide in due diversi cluster; questo indicherebbe che sono necessari ulteriori approfondimenti sulla filogenesi di questa specie. In conclusione, oltre a confermare la maggior efficacia del metodo di identificazione con la sequenza del gene EF-1 α, questo studio ha permesso di avere una visione più completa della distribuzione delle specie di Armillaria nella regione Trentino Alto Adige, in quanto gli studi precedenti condotti nel medesimo areale hanno interessato zone più ristrette e habitat specifici.
Le specie di Armillaria in Trentino Alto Adige: valutazione dei metodi di identificazione molecolare e analisi della distribuzione.
BRESCIA, FRANCESCA
2014/2015
Abstract
Armillaria is a white-rot basidiomycete affecting both timber and agronomic trees, which causes significant economic damages worldwide. In Europe five Armillaria species are known, but only two of them are particularly dangerous (A. mellea and A. ostoyae). Because of climate changes and recent forestry maintenance practices, the trees stress enhances the virulence and the spread of the pathogen. At present there aren’t effective means of control against Armillaria; it is only possible to prevent the disease or to treat it at early stages. There aren’t distinguishable symptoms, an early diagnosis is thus difficult to obtain. In addition, it is not easy to identify Armillaria at the species level, since identification with both morphologically methods and incompatibility tests (somatic and sexual) requires some months and often gives ambiguous results. It is therefore of primary importance the investigation of alternative methods to identify Armillaria. The present study concerns the Trentino Alto Adige region; 80 Armillaria basidiocarp samples were identified at the species level with molecular methods. The aim was to compare the identification effectiveness of two different sequences (ITS 1 and 4 and Elongation Factor-1 α). The identification with the EF-1 α gene sequence resulted in a higher precision and reliability compared with the one obtained with ITS gene sequence. This result is consistent with the phylogenetic trees built with the respective sequences. The distribution of the Armillaria species in Trentino Alto Adige was highlighted and a comparison with other previous studies was made. A. borealis (typical of cold environments) resulted as the most frequent species (25%) and it was found in the Bolzano province (high altitude habitats); A. gallica, A. cepistipes and A. ostoyae (22%, 21%, 19%) are following and at last A. mellea (10%) was found. No sample of A. tabescens (termophilic species typical of Mediterranean climate) was reported. It was possible to observe, both from the phylogenetic trees and from the specific primers results, that A. borealis splits into two different clusters. This could indicate that further investigations about this species phylogeny are requested. In conclusion the present study confirmed the superior effectiveness of the identification method based on EF-1 α sequence; furthermore, it allowed a more complete knowledge about the distribution of Armillaria species in Trentino Alto Adige region, since previous studies concerned more limited areas and specific habitats.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/22630