Divergent gene expression responses to salinity stress in 16 geographically diverse spinach genotypes

Authors: Sandhu, Devinder; Pudussery, Manju; WILLIAM, MARIA - University Of California, Riverside; KAUNDAL, AMITA - Utah State University; Ferreira, Jorge

Submitted to: ACS Agricultural Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2023
Publication Date: 8/30/2023
Citation: Sandhu, D., Pudussery, M.V., William, M., Kaundal, A., Ferreira, J.F. 2023. Divergent gene expression responses to salinity stress in 16 geographically diverse spinach genotypes. ACS Agricultural Science and Technology. 3(9):795-804. https://doi.org/10.1021/acsagscitech.3c00149.
DOI: https://doi.org/10.1021/acsagscitech.3c00149

Interpretive Summary: One of the challenges in growing enough food to feed our growing population is the lack of good-quality water for crops. Farmers might be tempted to use cheaper recycled water for their crops, but these waters often have a lot of salt in them, which can be harmful to the plants. While some studies have evaluated the effect of salinity on a limited number of spinach genotypes, there is a lack of comprehensive research that explores the performance of diverse genotypes and links their performance to genetic determinants. In this study, we evaluated 16 geographically diverse spinach genotypes for their salinity tolerance and showed that salinity tolerance varied considerably among different genotypes, allowing us to rank them based on their level of salinity tolerance. Different spinach genotypes varied in how they stored or excluded salt in different parts of the plant, explaining variations in their salinity tolerance. Gene expression analysis characterized genotypes based on specific traits involved in salinity tolerance. These traits include the ability of the roots to keep salt ions out, storing salt in the vacuole, moving ions from the roots to the shoots, maintaining a balance of salt in the plant, and getting rid of harmful molecules called reactive oxygen species. By combining the best traits of different types of spinach through crossbreeding and selection, new spinach varieties can be developed that are highly tolerant to salt. By identifying spinach genotypes that are more tolerant to salt, our study may help increase the profitability of farmers who use recycled water. Our research shows that farmers can choose the best types of spinach to grow in salty water and have a better chance of growing successful crops. Further, the results of this study will be beneficial for researchers interested in understanding how plants respond to salts and minerals.

Technical Abstract: 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.