|KAUNDAL, AMITA - Utah State University
|FOREST, THOMAS - University Of California
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/28/2020
Publication Date: N/A
Technical Abstract: Plants employ several strategies to cope with salinity stress and toxic ions. Understanding the roles of different component traits of plant salt tolerance mechanism is critical. We evaluated 16 commercial almond rootstocks under irrigation waters of 5 different salt compositions. An increased salinity from 1.4 dS m-1 (control) to 3 dS m-1 (treatments) caused significant reductions in survival rate, trunk diameter, chlorophyll SPAD (SPAD), photosynthetic rate (Pn), stomatal conductance (gs), transpiration (Tr) and water use efficiency (WUE) for most rootstocks. Our analysis suggested that mostly Na, and to a lesser extent, Cl concentration in irrigation water are the most critical ion toxicities for almond rootstocks. The top-performing rootstocks under salinity also had the least amount of tissue accumulation of Na and Cl, suggesting that ion exclusion may be the main component trait of the salt tolerance mechanism in almond. Furthermore, the expression analyses of 24 genes revealed that treatments, where Na and Cl were the main ions in irrigation water, led to the induction of most genes, suggesting the importance of both chloride and sodium toxicities during salt stress. Correlations among gene expression, trunk diameter, biochemical markers, and tissue ion concentrations allowed us to identify the component of salt tolerance mechanism that is the most critical in a particular genotype in almonds and that may be manipulated to improve its salt tolerance. Important genes involved in the salt tolerance mechanism were identified and the most tolerant rootstocks were selected. Genetic transformation of the Arabidopsis athkt1 knockout mutant with HKT1 ortholog (PpHKT1) from the almond rootstock ‘Nemaguard’ resulted in transgenic lines with significantly higher biomass, longer lateral roots, relatively lower electrolyte leakage, and high relative water content compared to athkt1 under salinity stress. This analysis confirmed that PpHKT1 can complement the salt tolerance function in the Arabidopsis mutant.