Fungal species involved in Kermes oak (Quercus coccifera L.) branch canker in Tunisia

Abstract: Since 2012, a severe and widespread decline and mortality affecting several of
Mediterranean forest species has been occurred throughout Tunisian forests. In 2017, field
surveys showed a progressive dieback of Quercus coccifera L. (kermes oak), including shoot
dieback, brown lesions on branches and innumerable pycnidia on infected tissues. For its
ecological interest, preservation of Q. coccifera as valuable evergreen forest tree must be of
great interest. However, information regarding kermes oak disease is still scarce. Hence, the
aims of this study were to characterize the fungal pathogens associated with Q. coccifera branch canker in two Tunisian forests and evaluate their virulence. Twenty-eight isolates were obtained from symptomatic kermes oak branches. Based on morphological features and phylogenetic analysis of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and partial sequence of the translation elongation factor 1-alpha gene (tef1-α) two fungal species namely Diplodia seriata and Pestalotiopsis biciliata were identified. Moreover, D. seriata species were the main fungi consistently obtained from symptomatic Q. coccifera branches. Pathogenicity tests carried out on asymptomatic detached branches confirmed the virulence of the two species. These findings confirm D. seriata and P. biciliata as fungal pathogens associated with kermes oak branch canker and dieback in Tunisia. To the best of our knowledge, these two plant pathogenic fungi are identified for the first time on kermes oak in Tunisia.