Rayda Siala¹, Ines Ben Chobba¹, Tatiana Vallaeys², Mohamed Ali Triki³, Mouna Jrad³, Manel Cheffi³, Imen Ayedi⁴, Amine Elleuch¹, Ahmad Nemsi⁵, Frederique Cerqueira⁶, Radhouane Gdoura⁷, Noureddine Drira¹, Néji Gharsallah¹

Biological control still remains an unexploited issue in southern countries such as Tunisia. Thus, the present study focused on the diversity of cultivable endophytic bacteria in the internal tissues (roots and leaves) of Tunisian date palm trees (Phoenix dactylifera L.). In order to assess their antagonistic potential towards date palm pathogens, particularly Fusarium. Indeed, the Genus Fusarium includes the causative agent of the Bayound disease, Fusarium oxysporum, a major treat for date production North Africa. Twenty two bacterial isolates presenting distinct colony morphology on TSA media were selected. The latter were characterized using Gram staining, biochemical tests, and molecular identification techniques based on 16S rRNA gene sequencing. Cultivable endophytic isolates were assigned into seven distinct groups. The species Arthrobacter agilis and Bacillus subtilis exhibited lasting antagonistic properties against a range of Fusarium species including the causing agent of the Bayoud disease, thus demonstrating their strong potential for future applications in the inoculation of date palm trees for biocontrol purposes. The isolates showed extracellular enzymatic activity including cellulase (76, 92%), protease (69, 23%) and amylase (38, 46%). This study thus demonstrates for the first time that the diversity of endophytic bacteria is abundant in date palm trees (Phoenix dactylifera L.) and could present varying biotechnological applications and particularly disease control.

palm date tree, endophytic bacteria, molecular identification, biocontrol, Fusarium spp., bayound deseases