The use of microorganisms to facilitate the growth of plants in saline soils

Worldwide, salinity is one of the most important abiotic stresses that limits crop growth and productivity. Ion imbalance and hyperosmotic stress in plants caused by high concentrations of salt often lead to oxidative stress conditions for plants. Soil salinization may be due to natural causes, and is common in the hot and dry regions of the world, or it may be a consequence of inadequate irrigation management practices. It has been estimated that around 20% of the world's cultivated lands and up to half of all irrigated lands are affected by high salinity. Moreover, at the present time, there is more arable land being lost through salinity than is gained through the clearing of forests. In this chapter, the ability of plant beneficial microorganisms, notably plant growth-promoting (PGP) bacteria and mycorrhizae, to facilitate plant growth in the presence of salt is reviewed and discussed. Particular attention is paid to the development of a fundamental understanding of precisely how these microorganisms enable plants to proliferate in the presence of otherwise inhibitory levels of salt. A better understanding of these mechanisms is likely to lead to the development of simple and practical approaches for dealing with this problem in the field.