Understanding the landscape of salt tolerance mechanism in alfalfa

Authors: Sandhu, Devinder; Ferreira, Jorge; CORNACCHIONE, MONICA - Estacion Experimental Agroindustrial Obispo Colombres (EEAOC); KAUNDAL, AMITA - University Of California - Cooperative Extension Service; Pudussery, Manju; Suarez, Donald

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/14/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Salinity is a major abiotic stress that limits plant growth and productivity globally. Salinity affects various physiological, biochemical, and metabolic processes resulting in decreased crop production. To tackle the salinity problem, it is important to link the biochemical and physiological responses with the underlying genetic determinants, which will be the key in developing genetic material tolerant to salt. Our studies with salinity effects on alfalfa (Medicago sativa) revealed that the selection based on total biomass and ion composition was highly efficient. Foliar leaf area, photosynthesis, transpiration, and stomatal conductance were reduced in most genotypes under salinity. Genes that play important roles in salt tolerance in alfalfa include SOS1, SOS2, SOS3, NHX1, AVP1, HKT1, P5CS1, HSP90.7 and HSP81.2. Gene expression analyses allowed us to classify genotypes based on their ability to regulate different components of the salt tolerance mechanism. Na+/H+ exchangers (NHX) that are known to play important roles in sequestration of Na+ into vacuoles and in keeping cytoplasmic Na+ concentration low also played critical role in alfalfa salt tolerance. Bioinformatics and phylogenetic analyses of Arabidopsis NHX genes enabled us to characterize corresponding genes in Medicago truncatula. Conservation of 12 transmembrane domains, an amiloride-binding motif, and 5 critical residues involved in Na+/H+ exchange among NHX proteins suggest that the ion exchange mechanisms in M. truncatula and Arabidopsis thaliana are highly conserved. Relatively smaller increases in Na+ accumulation, as compared to Cl-, in tissues of salt-treated plants were probably the result of an effective Na+ exclusion mechanism. As alfalfa is congeneric with M. truncatula, the knowledge acquired using M. truncatula as a model plant will help in characterizing salt tolerance responses in alfalfa. The knowledge generated with this research will aid alfalfa breeders to identify more salt-tolerant cultivars that may be used to develop new salt-tolerant germplasms that will thrive in marginal lands under poor-quality irrigation water.