Molecular characterization and pathogenicity of Diplodia corticola and other Botryosphaeriaceae species associated with canker and dieback of Quercus suber in Algeria

In Algeria cork oak forests are irregularly distributed in the northern regions along the Tell Atlas mountain range. Over the last few decades, severe tree decline and mortality events has been observed in several of the main cork oak forests. Since there is little information about the aetiology of this decline and given the high ecological and economic importance of cork oak ecosystems, a survey was carried out in six forests, M'sila and Hafir (northwestern Algeria), and Ksar Fatma, Haddada, An Zana and Oued El Hout (northeastern Algeria), to establish the fungal pathogens associated with cork oak branch diseases. Isolations from symptomatic branches of 88 declining trees yielded a total of 96 fungal isolates of which 69 belonged to three distinct genera of Botryosphaeriaceae, namely Diplodia, Dothiorella and Lasiodiplodia. On the basis of morphological features and DNA sequence data (ITS and tef1-), five species: Diplodia corticola, D. quercivora, D. sapinea, Dothiorella iberica and Lasiodiplodia exigua were identified. The geographical distribution and occurrence of the five species differed greatly among sites. The occurrence of both known lineages of D. corticola was also recognised. Pathogenicity trials showed that all the species assayed are pathogenic on cork oak and D. corticola proved to be the most aggressive.