Cork Oak Forests Soil Bacteria: Potential for Sustainable Agroforest Production

Abstract

Plant growth promoting rhizobacteria (PGPR) are in increasing demand due to their role in promoting sustainable practices, not only in agriculture but also in forestry. Keeping in mind the future application of PGPR for increasing cork oak sustainability, the aim of this study was to find cork oak PGPR isolates with increased nutrient solubilisation traits, able to promote root morphological changes and/or antagonize cork oak bark phytopathogens. Soils from three cork oak forests with distinct bioclimates (humid, semi-humid and semi-arid) were used for isolating bacteria. From the 7634 colony-forming units, 323 bacterial isolates were biochemically assayed for PGPR traits (siderophores production, phosphate solubilizing and organic acids production), and 51 were found to display all these traits. These PGPR were able to induce root morphological changes on Arabidopsis thaliana, like suppression of primary root growth, increase of lateral roots or root hairs formation. However, the most proficient PGPR displayed specific ability in changing a single root morphological trait. This ability was related not only to bacterial genotype, but also with the environment where bacteria thrived and isolation temperature. Bacteria from semi-arid environments (mainly Bacillus megaterium isolates) could hold a promising tool to enhance plant development. Other isolates (Serratia quinivorens or B. cereus) could be further explored for biocontrol purposes.

Bacillus subtilis HG-15, a Halotolerant Rhizoplane Bacterium, Promotes Growth and Salinity Tolerance in Wheat (Triticum aestivum)

“…Soil salinization reduces the energetic state of rhizosphere soil water, causing the osmotic pressure of the soil solution to exceed the normal osmotic pressure in plant cells, which results in osmotic stress [ 5 ]. This leads to changes in the length, density, and structure of plant roots, reducing the uptake of soil water and nutrients, causing the plants to enter a state of physiological drought, and slowing or even killing the plant [ 6 ]. Oxidative stress causes damage to the cell membranes and photosynthetic system [ 7 ].…”

Probing the potential of salinity-tolerant endophytic bacteria to improve the growth of mungbean [Vigna radiata (L.) Wilczek]

“…P. extremorientalis improved plant growth under salt stress by reducing harmful effects of salt ( Egamberdieva et al, 2016 ). Recently, researchers have revealed the existence of S. quinivorans in the oak, Petroselinum crispum and Picrorhiza kurroa ( Kumar et al, 2021 ; Reis et al, 2021 ; Chlebek et al, 2022 ). Novel plant-bacterial associations might be due to the changes in environmental conditions.…”