The Effect of Date Palm Genotypes on Rhizobacterial Community Structures under Saline Environments

Abstract

Some genotypes of date palms (Phoenix dactylifera L.) are salt-tolerant; however, salinity significantly affects others. This study aimed to determine the root epiphytic bacterial contributions to the salt tolerance mechanism in the date palm and to verify if the salt-tolerant “Umsila” and the salt-susceptible “Zabad” cultivars have different bacterial communities. Therefore, the epiphytic bacterial community structures were investigated in both cultivars when grown under control and salinity conditions. The proximal soils of the roots were collected, the DNA was extracted, and a culture-independent approach using Illumina® MiSeq™ sequence analysis was carried out to identify the changes in the bacterial community structures in the soil samples due to the changes in salinity and the genotypes of the plants based on 16S rRNA gene sequencing. While salt tolerance response differences were evident between the two cultivars, the 16S rRNA gene sequencing results revealed 771 operational taxonomic units (OTUs), including 62 that were differentially accumulated in response to salinity. The ordination analysis showed significant (p = 0.001) changes among the communities in response to salinity in both cultivars. However, the results showed that the two cultivars had distinct bacterial communities when grown under controlled conditions, whereas they had a more similar bacterial community structure when grown under salinity conditions. The plant genotype does not affect the epiphyte bacterial community structure under salinity, probably because salinity affects the plant-microbe interaction similarly in both cultivars. Also, the identified rhizospheric bacteria are not directly associated with the root’s physiological processes in response to salinity.

The Effects of Salinity and Genotype on the Rhizospheric Mycobiomes in Date Palm Seedlings

“…Advanced DNA sequencing technologies, such as NGS, have the potential to enhance the efficient identification and subsequent successful isolation of microbial organisms [ 29 ]. Comparative microbiome analysis is a versatile means of identifying microbes that grow under conditions of high salinity in the rhizosphere of a specific plant genotype [ 22 ]. Therefore, this study employed NGS technology to study the mycobiomes of two distinct genotypes of date palms, each with different salinity tolerance capacities, to characterize mycobiomes in date palms.…”

“…A previous study on the rhizobacterial communities of the same date palm cultivars (‘Umsila’ and ‘Zabad’) found that the plant genotype did not significantly impact the epiphyte bacterial community structure under salinity stress [ 22 ]. In contrast, the results reported here reveal that the fungal communities are affected by salinity in the mycobiomes of both date palm genotypes.…”

“…The date palm seeds utilized in this study belong to the salt-tolerant ‘Umsila’ and salt-susceptible ‘Zabad’ cultivars, which resulted from the cross-pollination of a unique pollen genotype and were acquired from the experimental agriculture station of Sultan Qaboos University in Muscat, Oman. Prior to planting, the seeds underwent a series of treatments to ensure their sterility and optimize their germination, following a previously described protocol [ 22 ]. Briefly, the seeds were soaked in sterile distilled water overnight to remove any remaining fruit tissues.…”

“…The endophytic microbiota associated with date palms has been previously investigated to elucidate its role in salt tolerance, resulting in the identification of diverse bacterial and fungal species that respond to abiotic stresses [ 20 , 21 ]. Recent research has demonstrated distinct variations in the epiphyte bacterial community structures between two date palm genotypes with different salinity tolerances under optimal growth conditions [ 22 ]. However, these differences tend to decrease when the plants are exposed to salinity stress, suggesting the existence of common salt-tolerant bacterial species capable of colonizing the roots of various date palm genotypes [ 22 ].…”

“…Recent research has demonstrated distinct variations in the epiphyte bacterial community structures between two date palm genotypes with different salinity tolerances under optimal growth conditions [ 22 ]. However, these differences tend to decrease when the plants are exposed to salinity stress, suggesting the existence of common salt-tolerant bacterial species capable of colonizing the roots of various date palm genotypes [ 22 ].…”