Water pH, not soil pH, alters bacterial community structural pattern and nitrogen cycling pathways in date palm (Phoenix dactylifera L.) roots and bulk soil under freshwater irrigation regime

Abstract

Date palms are widely cultivated in arid agroecosystems, where knowledge of irrigation water effect on their soil and root-associated bacterial communities is limited. Using 16S rDNA metabarcoding, we studied soil and root-associated bacterial communities of date palms growing in United Arab Emirates. Overall, 12.18% of bacterial operational taxonomic units (OTUs) were unique to roots, whereas 41.55% were specific to soil. The bacterial diversity was lower in root and community patterns were distinct between compartments, wherein irrigation water pH was a key structuring factor in both compartments, while salinity (electrical conductivity) was important only in the soil. Co-occurrence network analysis revealed a decrease in complexity in the soil–root continuum, and specific taxa/modules also varied with water pH. We observed a higher abundance of endophyte–saprotroph (Bacillus, Streptomyces and Dongia) dual-role OTUs in both compartments, possibly involved in nutrient mobilisation and plant growth. Based on PICRUSt and trait-based analyses, we showed that these OTUs are putatively involved in the nitrogen cycle (nitrification, denitrification, and assimilatory nitrate reduction). Taken together, we suggest that irrigation water pH, not soil pH, transiently affects belowground bacterial communities and selects bacteria in specific pH ranges, which may be important for nutrient cycling (i.e. nitrogen cycle) in arid agroecosystems.

Response of bacterial community metabolites to bacterial wilt caused by Ralstonia solanacearum: a multi-omics analysis

“…For example, MND1 is an ammonia-oxidizing bacterium that affects nutrient absorption in plants ( Wang et al., 2022c ) and inhibits pathogens ( Yang et al., 2023b ). Dongia is considered to be involved in the soil nitrogen cycle, which may synergistically improve soil available nutrients and root uptake, promoting plant growth ( Wang et al., 2022a ; Sanka Loganathachetti and Mundra, 2023 ). Nitrospira was reported to be involved in the degradation and cycling of soil organic matter and increasing soil pH, thereby improving plant stress resistance of soil acidification and nutrient absorption ( Hu et al., 2021 ).…”

Harnessing rhizospheric core microbiomes from arid regions for enhancing date palm resilience to climate change effects

“…Indeed, date palms are adapted to arid and semi-arid regions. They withstand moderately alkaline soils, with a pH ranging from 7 to 8.5, but extremely high alkalinity can be detrimental to their growth (Alotaibi et al, 2023;Sanka Loganathachetti and Mundra, 2023). They are adapted to soils with low organic matter levels, ranging from 0.1 to 1 (Mlih et al, 2016(Mlih et al, , 2019, while proper fertilization is essential to ensure their optimal growth.…”

“…Furthermore, date palms exhibit a notable tolerance to salinity levels, commonly ranging from 4 to 8 dS/m or even higher under specific conditions (Muller et al, 2017;Alotaibi et al, 2023). Nevertheless, the irrigation of date palm with saline groundwater, due to water scarcity, is a common practice in the MENA regions, which threatens the sustainability of date palm cultivation (Shamim et al, 2022;Sanka Loganathachetti and Mundra, 2023).…”