Divergent Gene Expression Responses to Salinity Stress in 16 Geographically Diverse Spinach Genotypes

Salinity stands as a critical abiotic stress factor,
posing significant
challenges to global agricultural productivity. However, there is
no comprehensive study that simultaneously investigates multiple spinach
genotypes; integrates assessments of various parameters like biomass
yield, ion uptake, and partitioning; and conducts genetic characterization
of salinity tolerance mechanisms. To address this gap, we conducted
a greenhouse experiment with 16 spinach genotypes, from diverse geographical
regions, irrigated with saline waters of 1.87 and 23.3 dS m–1. The salt tolerance index for shoot biomass exhibited significant
variability among the genotypes, with 'Dikenli', 'Victoria',
and 'Cornell
ID #148' being the top performers and 'Cornell ID #87',
'Gazelle',
and 'Polag Benaresi' being the bottom performers. Under
high salinity,
on average, plants accumulated 25-fold higher Na and 8.5-fold higher
Cl in leaves compared to the control. Leaves accumulated 2.4-fold
more Na and Cl than roots under salinity compared to the control.
Expression analyses of specific genes in roots and leaves provided
insights into Na+/Cl– efflux, vacuolar
sequestration, root-to-shoot movement, ion homeostasis, and scavenging
of reactive oxygen species. Our results demonstrate the importance
of screening geographically diverse genotypes and considering multiple
traits when selecting genotypes for salt tolerance.