Molecular analysis of wrky trancription factors in banana (Musa acuminata cv. Berangan) primed with plant growth promoting bacteria / Abdussabur M Kaleh

Abdussabur , M Kaleh (2024) Molecular analysis of wrky trancription factors in banana (Musa acuminata cv. Berangan) primed with plant growth promoting bacteria / Abdussabur M Kaleh. PhD thesis, Universiti Malaya.

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Abstract

Saline soils pose a significant threat to food security, necessitating the exploration of solutions. In this study, halotolerant bacteria were isolated from a Malaysian mangrove forest and their effects on banana plantlets under salt stress were investigated. Among the collected isolates, three rhizobacterial strains (RB1, RB3, and RB4) and three endophytic bacterial strains (EB1, EB2, and EB3) exhibited the best performance in promoting plant growth. These strains, identified as Bacillus sp. and Pseudomonas sp., were further analyzed. Scanning electron microscopy confirmed their successful colonization of banana plantlet roots. When subjected to salt stress, the colonized plantlets, particularly those with strains EB3 and RB3, demonstrated improved growth, increased levels of chlorophyll, carotenoids, and proline, as well as reduced malondialdehyde content, reactive oxygen species generation, and electrolyte leakage. The activity of antioxidant enzymes was also enhanced in the presence of strains EB3 and RB3. These findings highlight the multifunctional plant growth-promoting activity of halotolerant Bacillus and Pseudomonas strains from the mangrove, offering potential for mitigating salt stress in bananas. Furthermore, a plant-growth promoting bacterial consortium comprising halotolerant Bacillus sp. and Pseudomonas sp. was evaluated for its priming effect on banana plants subjected to abiotic (salinity) and biotic (Foc-TR4) stresses. Primed banana plants exhibited improved growth parameters, including plant height, root length, and biomass, along with enhanced physiological characteristics such as relative water content, chlorophyll, and carotenoid contents, compared to non-primed plants under stress. Lipid peroxidation was reduced, and proline levels and antioxidant enzyme activities were increased in primed plants. In salt-stress conditions, primed plants showed elevated levels of K+, Ca2+, and Mg2+ ions, and reduced levels of Cl- and Na+. Under Foc-TR4 stress, primed plants demonstrated significant enhancements in total soluble phenolics, lignin content, and defense-related enzyme activities. Additionally, the expression analysis of stress-responsive MaWRKY genes revealed their upregulation in primed banana plants under salt and Foc-TR4 stresses. These findings highlight the effectiveness of the PGPB consortium in promoting banana plant growth and priming WRKY-mediated protection against abiotic and biotic stresses. In conclusion, the utilization of halotolerant Bacillus and Pseudomonas strains from mangroves as plant growth-promoting bacteria shows promise in alleviating salt stress in bananas. The priming effect of the bacterial consortium enhances plant growth, physiological parameters, ion balance, and defense mechanisms against abiotic and biotic stresses. These findings contribute to the exploration of microbial strategies for improving banana resilience and provide insights into the potential applications of halotolerant microbes in salt-stress tolerance enhancement in plants.

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