A critical look at plant response to salinity/sodicity and implication for global food security

Authors: Ferreira, Jorge; Suarez, Donald; Sandhu, Devinder

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/4/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Salinity is the second most threatening abiotic stress for agriculture and sustainable food production. The increasing demand for food and fresh water will lead to unsustainable agriculture in arid and semiarid regions. Although some crops can be irrigated with degraded saline waters, most are sensitive to excess salts. Thus, we must understand which crops we can resort to, how they respond to salinity, and how to minimize soil salinization triggered by excessive irrigation and fertilization of crops, mainly where rainfall is scarce. In the past 30 years, molecular genetics identified genes associated with salt tolerance, but the complexity of salinity tolerance mechanisms makes impactful advances challenging. This chapter discusses historical aspects of salinity, its effects on productive agriculture, crop yields as an indicator of excessive salinity, the importance of the balance of essential minerals in plant shoots, and other aspects of crop response to salinity. The US Salinity Laboratory is collaborating with plant breeders and national and international scientists to test new crop genotypes for salinity tolerance and generate the best options for an uncertain future of climatic changes. Salinity tolerance and response in plants are complex issues that can only advance through a multipronged collaboration among environmental and soil sciences, symbiotic microbes, water chemistry, plant physiology and biochemistry, molecular genetics, and breeding. This chapter will aid students and researchers in advancing their knowledge on plant responses to salinity stress and considering the implications of salinity to global food security.

Technical Abstract: Salinity is the second most threatening abiotic stress for agriculture and sustainable food production. Increasing demands for food and fresh water have resulted in unsustainable freshwater consumption in arid and semiarid regions, primarily for agricultural production. In most instances, there are sufficient volumes of brackish water and treated municipal wastewater to sustain essential agricultural production. However, for each crop and water source, we need to determine the factors limiting the use of these waters, be it ion imbalances, ion toxicities, osmotic stress, or production under unfavorable soil conditions, such as loss of infiltration and aeration resultant from the use of sodic waters. Characterization of crop salt tolerance and ranking of species and cultivars is necessary for the successful use of brackish and saline waters. This requires experiments with multiple salinity levels that consider the whole crop cycle to develop curves that describe plant salinity response and detailed information about the soil-water salinity of the experiment. Our experience has also shown that previous publications on crop salt-tolerance threshold must be updated to accommodate the thresholds shown by new crop cultivars, which are, sometimes, two- to four-fold more salt-tolerant, although they have not been bred for salt tolerance. Recently there has been great progress in identifying genes associated with salt tolerance that led to the identification of different component traits involved in salinity tolerance, including ion efflux from roots to the soil, ion sequestration into the vacuoles, root-to-shoot movement of ions, tissue tolerance and the homeostasis of essential mineral ions. Characterization of different genotypes based on component traits of salinity tolerance is essential for breeding new crop cultivars tolerant to salinity. Plant salinity tolerance and responses are complex issues that can only advance through a multipronged collaboration among researchers from different environmental sciences, including soil, symbiotic microbes, water chemistry, plant physiology and biochemistry, molecular genetics, and breeding. This chapter discusses plant responses to salinity stress and the implications of salinity on global food security.