Mangroves, dominating tropical intertidal zones and estuaries, are among the most salt tolerant plants, and propagate through reproductive units called propagules. Similarly to plant seeds, propagules may harbor beneficial bacteria. Our hypothesis was that mangroves, being able to grow into seawater, should harbor bacteria able to interact with the host and to exert positive effects under salt stress, which could be exploited to improve crop production. Therefore, we isolated bacterial endophytes from mangrove propagules with the aim to test whether these bacteria have a beneficial potential on their natural host and on different crops such as barley and rice, cultivated under salt stress. The 172 bacterial isolates obtained were screened for plant growth promotion (PGP) activities in vitro, and the 12 most promising isolates were tested on barley under non-axenic conditions and salt stress. Gordonia terrae KMP456-M40 was the best performing isolate, increasing ear weight by 65%. Based on the in vivo PGP activity and the root colonization ability, investigated by fluorescence in situ hybridization and confocal microscopy, three strains were additionally tested on mangrove propagule germination and on rice growth. The most effective strain was again G. terrae KMP456-M40, which enhanced the root length of mangrove seedlings and the biomass of salt-stressed rice under axenic conditions up to 65% and 62%, respectively. We demonstrated that propagules, the reproductive units of mangroves, host beneficial bacteria that enhance the potential of mangrove seedlings establishment and confer salt tolerance to cereal crops.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2018-CARF-1973
Acknowledgements: RS and MC acknowledge Karl-Heinze Kogel (Giessen) for the use the confocal microscope at the Institute of Phytopathology, JLU-Giessen. The research leading to these results received funding from the European Union's Seventh Framework Programme under grant agreement no 311975 (MACUMBA) and from the European Union's Horizon 2020 Research and Innovation program under Grant Agreement no 688320 (MADFORWATER). This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) and the Office of Sponsored Research (OSR) under Award No. OSR-2018-CARF-1973 to the Red Sea Research Center. RS received a “Master Thesis Scholarship” from the University of Milan. FM acknowledges personal support from the project “Unveiling plant-bacterium interaction for agriculture and bioremediation (NURTURE)” (Piano di Sostegno della Ricerca 2015–2017: Linea 2 - Dotazione annuale per attività istituzionali).