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Title: Evaluation and expression analysis of alfalfa genotypes in response to prolonged salt stress

Author
item Sandhu, Devinder
item CORNACCHIONE, MONICA - National Institute Of Agricultural Technology(INTA)
item Ferreira, Jorge
item Suarez, Donald

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/6/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Salinity is one of the most important abiotic stresses that adversely affect plant growth and productivity globally. In order to tackle this complex problem, it is important to link the biochemical and physiological responses with the underlying genetic mechanisms. In this study, we used 12 previously selected plants for different levels of salt tolerance, cloned them and tested them under long term salt treatment. Salt tolerance index for these genotypes ranged from 0.39 to 1.0. The most tolerant genotypes SISA 14 (G03), AZ-90 ST (G10) and SISA 14 (G08) were among top performers for the total biomass. With respect to the control, salinity decreased the shoot height and the number of shoots up to 34 % and 49%, respectively. SISA 14 (G03) and AZ-90 ST (G10) showed least effect on height and number of shoots under salt stress. All genotypes exhibited increased shoot Na and Cl concentrations under salinity. SISA 14 (G03) was among the genotypes with smallest increase in shoot Na concentration and stored least amount of shoot Cl under salt treatment. Decrease in shoot K concentration did not correlate well with salt tolerance. There was a little effect of salinity on Ca, Mg, P, Fe and Cu concentrations in shoots. In contrast, there were significant increases in in shoot Mn and Zn concentrations under salt stress. Salinity reduced the foliar area, photosynthesis (Pn), transpiration (Tr) and stomatal conductance (Gs) in leaves. Interestingly, SISA 14 (G03), which was a top performer for salt tolerance, was among the low performers for Pn, Tr and Gs. Interestingly, salinity increased the chlorophyll content in all genotypes. In an effort to understand the genetic mechanisms regulating salt tolerance, expression of 16 putative genes involved in salt stress was studied in the root and leaf tissues of the 12 genotypes grown in control and salt treatments. Genotypes Cuf 101 (G02), SISA 14 (G03), AZ-90 ST (G10) and Salado (G12) showed significant upregulation in roots for genes (SOS1, SOS2 and SOS3) involved in ion efflux from root to soil. All five genes (NHX1, NHX2, ATPase, SKIP1 and AVP1) known to be involved in sequestration of Na in vacuoles were strongly induced by salt in roots of Salado (G12). Only one gene out of five showed upregulation in roots of SISA 14 (G03). Both the genes involved in retrieval of Na from xylem, HKT1 and AKT1, were induced by salt stress in roots of AZ-90 ST (G10) and Salado (G12). Analysis of genes involved in increased tissue tolerance (AP2, ERF1, P5CS, HSP90, SGP29) showed upregulation in the leaves of Cuf 101 (G02), SISA 14 (G03), SW9720 (G05), SISA 9 (G06), SISA 10 (G09). Expression analysis of genes allowed us to classify genotypes based on their ability to regulate different components of salt tolerance mechanism and will let us combine the components from different genotypes using genetic crosses.