Halophytes and their rhizosphere relationships: tools for the adaptation of

traditional agriculture to climate change

The latest report of the Intergovernmental Panel on Climate Change (IPCC) predicts, along with increasing atmospheric CO2, increases in temperature, in the duration and intensity of drought, in soil salinization, etc. This change, which will determine the productivity of agricultural systems, especially in arid and semiarid regions of the world, runs parallel to the rise in world population and the need for resources. Consequently, climate change emerges as one of the biggest challenges for sustaining global food security and it is therefore crucial to find options to mitigate its effects on agricultural production. One of such options is the use of alternative crops; species capable of growing in hostile environments (salinity and water deficit).

In this regard, halophyte species have been proposed for animal feed or human consumption, because they present tolerance mechanisms against environmental stress, high productivity, and exceptional nutritional values. However, we are not certain about the physiological response of these plants to future climate reality, because to date there has been no research on the synergy of environmental factors that will vary as a result of climate change (no more than two factors simultaneously). Nor there have been studies on the interactions of halophytes with some beneficial bacteria associated with the rhizosphere, collectively called plant growth promoting rhizobacteria (PGPR), which positively affect plants by improving root growth or strengthening tolerance to environmental stressors. Thus, inoculations with PGPR consortia are a biotool for adapting traditional farming practices to future climate reality.

Hence, the objective of this proposal is to demonstrate that inoculation with native bacteria with PGP properties obtained from the rhizosphere of different halophytes (and therefore adapted to salinity, drought, high temperatures, etc.), could enhance the growth of other halophytes of commercial interest and traditional crops in synergistic conditions of elevated CO2, increased temperature, salinity and water deficit. A multidisciplinary approach by means of microbiological, physiological, biochemical and molecular studies will be used to achieve six specific objectives: 1) study the present microbial biodiversity in the rhizosphere of five halophytes, representatives of the Atlantic marshes of the Iberian Peninsula, and establish microbial consortia; 2) study the growth and physiological response of the halophyte Salicornia ramosissima, selected for its commercial interests (practical crop, multifunctional), inoculated with established consortia in synergistic conditions of elevated CO2 , increased temperature, salinity and water deficit; 3) study the molecular mechanisms of S. ramosissima involved in its response and 4) analyze their quality (nutritionally valuable metabolites); 5) evaluate the growth and physiological response of rice, wheat, corn and strawberry inoculated with the bacterial consortia in the prospect envisaged in a climate change scenario; and 6) develop a catalogue for the transfer of results, as they constitute an innovative solution with a high biotechnological potential.

KEY WORDS: Crop, Growth, Halophyte, Inoculum, Metabolites, Nutrients, Physiological response, Rhizobacteria, Transcriptomics

Demonstrate that inoculation with bacteria with plant growth promoting properties (PGP), obtained from the rhizospheres of different halophyte species, would improve the growth of other halophytes of commercial interest and of traditional crops under synergistic conditions of high CO2, temperature increase , salinity and water deficit.

The general objective of this project is based on six specific objectives (Figure 1):

1) Study the microbial biodiversity present in the rhizosphere of several halophytes. Isolation and selection of rhizobacteria and establishment of microbial consortia 

2) Study the growth and physiological response of S. ramosissima, inoculated with established consortia, under synergistic conditions of high CO2, temperature increase, salinity and water deficit.

3) Study the molecular mechanisms of S. ramosissima, involved in their response to synergistic conditions of high CO2, temperature increase, salinity and water deficit, both inoculated and inoculated.

4) Analyze the quality of S. ramosissima inoculated in a Climate Change scenario.

5) Evaluate the growth and physiological response of traditional crops inoculated with bacterial consortia in the scenario provided by Climate Change.

6) Prepare a catalog with the bacterial consortia to be applied to each crop, of S. ramosissima or traditional, to optimize its growth and physiological state under the conditions foreseen by the Climate Change.