An Overview of the Genetics of Plant Response to Salt Stress: Present Status and the Way Forward

Abstract

Salinity is one of the major threats faced by the modern agriculture today. It causes multidimensional effects on plants. These effects depend upon the plant growth stage, intensity, and duration of the stress. All these lead to stunted growth and reduced yield, ultimately inducing economic loss to the farming community in particular and to the country in general. The soil conditions of agricultural land are deteriorating at an alarming rate. Plants assess the stress conditions, transmit the specific stress signals, and then initiate the response against that stress. A more complete understanding of plant response mechanisms and their practical incorporation in crop improvement is an essential step towards achieving the goal of sustainable agricultural development. Literature survey shows that investigations of plant stresses response mechanism are the focus area of research for plant scientists. Although these efforts lead to reveal different plant response mechanisms against salt stress, yet many questions still need to be answered to get a clear picture of plant strategy to cope with salt stress. Moreover, these studies have indicated the presence of a complicated network of different integrated pathways. In order to work in a progressive way, a review of current knowledge is critical. Therefore, this review aims to provide an overview of our understanding of plant response to salt stress and to indicate some important yet unexplored dynamics to improve our knowledge that could ultimately lead towards crop improvement.

Salinity and crop yield

“…It is important to note that salinity can cause crop yield losses even though the effects of salinity may not be obvious. Both salt tolerance and sensitivity of a specific crop depend on its ability to extract water and nutrients from saline soils and to avoid excessive tissue accumulation of salt ions (Ahmad et al 2017;Khan et al 2017;Kaleem et al 2018) The majority of vegetable crops is highly salt sensitive. In the model of Maas & Hoffman (1977), relative crop yield is not affected until a salinity threshold (ECt) is exceeded, according to the following equation: Y = 100 -S (EC e -EC t ), where Y is the relative crop yield with 100 being the maximum yield, EC e is the salinity of saturated soil extract, and EC t (dS m À1 ) is the threshold defined as the value of the electrical conductivity (EC) that is expected to cause the initial significant reduction in the maximum expected yield, and S is the slope that represents the percentage of yield expected to be reduced for each unit of added salinity above the EC t .…”

Comparative transcriptome analysis reveals synergistic and disparate defense pathways in the leaves and roots of trifoliate orange (Poncirus trifoliata) autotetraploids with enhanced salt tolerance

“…is widely used as a rootstock for the citrus industry due to its excellent traits, including cross compatibility with other related genera 31 and superior resistance to cold stress and several diseases 32,33 . However, it is generally sensitive to salt 34,35 , limiting its application in regions with saline soils. Accordingly, a major goal for trifoliate orange improvement is to increase its salt tolerance.…”

The role of gibberellin synthase gene GhGA2ox1 in upland cotton (Gossypium hirsutum L.) responses to drought and salt stress

“…Recent advances have shown that signal transduction of salt and drought stress includes osmotic as well as ionic homeostasis signaling pathways along with growth‐regulating pathways. The signaling adaptability mechanism mainly includes hormonal regulation through abscisic acid (ABA) signaling pathway and GAs pathway . The results showed that GAs are also involved in the regulation when subjected to abiotic stress .…”

“…The interaction between DELLA protein and GID1 led to the degradation of these proteins, which causes the activation of GAs signaling pathways and their functions . Under stress conditions, the mode of DELLA protein enhances plant survival by reducing the accumulation of reactive oxygen species, which is a substance that mediates cell death . Once GID1 was combined with active GAs, the GAs signal was transmitted to DELLA protein to regulate the expression of GAs synthesis genes.…”