DefinePK

Abstract

Background: Cacti thrive in arid and nutrient-deficient environments largely due to their association with endophytic bacteria, which enhance plant resilience by promoting growth and mitigating stress. These bacteria are known to facilitate nutrient uptake, synthesize phytohormones, and confer resistance against abiotic stressors. Despite their ecological significance, endophytic communities in cacti remain underexplored compared to agricultural crops. Understanding their diversity and functional roles is essential for advancing sustainable agriculture in stress-prone environments.
Objective: To evaluate the diversity and plant growth-promoting (PGP) characteristics of endophytic bacteria isolated from various cactus species and to identify strains with potential applications in arid-land agriculture.
Methods: Plant samples from diverse cactus species were collected from the Hazara Division, Pakistan. Following surface sterilization, endophytic bacteria were isolated using culture-dependent methods. Morphological, biochemical, and molecular characterizations, including 16S rRNA sequencing, were performed. The isolates were tested in vitro for nitrogen fixation, phosphate solubilization, indole-3-acetic acid (IAA) production, and tolerance to abiotic stressors such as high salinity and temperature.
Results: A total of 120 bacterial isolates were recovered, with 42% belonging to Proteobacteria, 31% to Firmicutes, and 18% to Actinobacteria. Approximately 68% exhibited nitrogen-fixing activity, and 59% demonstrated phosphate-solubilizing potential. IAA production ranged from 3–58 μg/mL, with highest levels observed in Bacillus amyloliquefaciens. Around 43% tolerated 10% NaCl, and 28% remained viable after 48 hours at 45°C. Notably, 34% of strains exhibited three or more PGP traits.
Conclusion: Cactus-associated endophytic bacteria exhibit high diversity and multifunctional PGP capabilities, making them promising candidates for bioinoculants in arid and semi-arid agriculture. Their ability to enhance plant fitness under environmental stress positions them as valuable tools for sustainable farming in water-limited regions.