Date of Award
Master of Science (MS)
Dr. Khaled El-Tarabily
Date palm trees suffer from many various serious diseases, including sudden decline syndrome (SDS). External symptoms were characterized by whitening on one side of the rachis, progressing from the base to the apex of the leaf until the whole leaf dies; while the internal disease symptoms included reddish roots and highly coloured vascular bundles causing wilting and death of the tree. Although three Fusarium spp. (F. oxysporum, F. proliferatum and F. solani) were isolated from diseased root samples, the fungal pathogen F. solani was associated with SDS on date palm in the United Arab Emirates (UAE). Fusarium spp. were identified based on their cultural and morphological characteristics. The internal transcribed spacer regions and large subunit of the ribosomal RNA (ITS/LSU rRNA) gene complex of the pathogens was further sequenced. Pathogenicity assays and disease severity indices confirmed the main causal agent of SDS on date palm in the UAE as F. solani. In order to control SDS in the UAE using biological control methods, endophytic actinobacteria were isolated from within the roots of date palm in the UAE and were evaluated for their potential to secrete antifungal metabolites and cell-wall degrading enzymes that can inhibit the pathogen growth in vitro. The strongest two inhibitory endophytic biocontrol agents that produced cell wall degrading enzymes and lysed the hyphae of F. solani (BCA1) or secreted diffusible antifungal metabolites (BCA2) which completely inhibited F. solani growth were also tested under greenhouse conditions to study their effects on SDS reduction. The biocontrol agent BCA2 which produced only diffusible antifungal metabolites and without the production of cell wall degrading enzymes was significantly more effective in reducing the incidence and severity of SDS compared to biocontrol agent BCA1 which produced only cell wall degrading enzymes and without the production of diffusible antifungal metabolites. This study demonstrated the superiority of antagonistic endophytic actinobacteria (BCA2) capable of producing diffusible antifungal metabolites compared to antagonistic endophytic actinobacteria (BCA1) capable of producing cell wall degrading enzymes in reducing the severity of SDS on date palm under greenhouse conditions.
Shambeh Alblooshi, Aisha Abdullah Darwish, "BIOLOGICAL CONTROL OF FUSARIUM WILT IN DATE PALM (PHOENIX DACTYLIFERA L.) IN THE UNITED ARAB EMIRATES BY ENDOPHYTIC ACTINOBACTERIA" (2020). Theses. 902.