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Distribution of potential halophytes associated HT-PGPB from the mangroves of Terengganu

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1 Han Meng Teo, Aziz Ahmad, Lee Chuen Ng *
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1 Laboratory of Pest, Disease and Microbial Biotechnology (LAPDiM), Faculty of Fisheries and Food
Science (FFFS), Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia.
2 Biological Security and Sustainability Research Group, Faculty of Science and Marine Environment,
Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia.

* Corresponding author: nglee@umt.edu.my

Abstract:

The utilization of halotolerant plant growth-promoting bacteria (HT-PGPB) as bio-inoculant to improve
crop performance and mitigate salinity stress is gaining traction due to the raised awareness of
sustainable agriculture and rising salinization issues. However, the distribution of these HT-PGPB
concerning the mechanisms that enable them to act as bio-fertilizers, bio-stimulant and bio-pesticides
is still unexplored. Hence, this study aimed to discover the distribution of potential halophyte-associated
HT-PGPB from the mangroves of Terengganu. HT-PGPB was isolated by serial dilution of rhizosphere
soil and root samples sampled from Kuala Nerus, Setiu, Merang, and Marang. These isolates were
screened for plant growth promoting (PGP) and salinity defence (SD) traits. The testing revealed that
the sampled halophytes harboured potential halotolerant bacteria with diverse characteristics and
morphologies. The initial screenings showed that 32 % of the isolated rhizobacteria and 43 % of
endophytes could survive on high salinity of 2.0 M NaCl. These halo-bacteria were then further in vitro
screened for PGP traits, such as Biological Nitrogen Fixation (99.5 % of halo-rhizobacteria and halo-
endophytes), IAA production (13 % of halo-rhizobacteria and 11 % halo-endophytes), phosphorus
solubilization (32 % of halo-rhizobacteria and 22 % halo-endophytes), and siderophore synthesis (65 %
of halo-rhizobacteria and 34 % halo-endophytes). The halo-bacteria with multiple PGP traits can
potentially colonize and instil Induced Systemic Tolerance among other glycophytic crops, enabling the
cultivation of salt-sensitive crops even under growth-inhibiting saline soils. Therefore, current results
support the distribution and concept of HT-PGPB that thrives in high salinity conditions with multiple
PGP and salinity defence traits.

Keywords: Halophytes, Plant growth-promoting bacteria, Rhizobacteria, Endophytes