Contrasting responses of guar genotypes shed light on multiple component traits of salinity tolerance mechanisms

Authors: Sandhu, Devinder; PALLETE, ANDREW - University Of California; Pudussery, Manju; GROVER, KULBHUSHAN - New Mexico State University

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2021
Publication Date: 5/26/2021
Publication URL: https://handle.nal.usda.gov/10113/7406716
Citation: Sandhu, D., Pallete, A., Pudussery, M.V., Grover, K.K. 2021. Contrasting responses of guar genotypes shed light on multiple component traits of salinity tolerance mechanisms. Agronomy. 11(6). Article 1068. https://doi.org/10.3390/agronomy11061068.
DOI: https://doi.org/10.3390/agronomy11061068

Interpretive Summary: Guar is an important fodder crop that is rich in proteins. Besides, it is an important source of guar gum, which is used as a thickening agent in various food, as well as to increase the viscosity of water used to extract oil and natural gas from tight rock formations. Due to its ability to tolerate various abiotic stresses, guar can be successfully grown in water deficit conditions and/or with degraded waters, which are generally high in salt contents. In this investigation, we aimed at understanding the importance of different component traits regulating salinity tolerance in guar. Field evaluations of four genotypes under non-saline conditions showed comparable performance of these genotypes. Greenhouse experiments uncovered salt-tolerant and salt-sensitive genotypes. Salt-tolerant lines maintained low leaf sodium and chloride concentrations under salinity as compared to the salt-sensitive lines. The relative leaf potassium concentrations under salinity compared to control was significantly higher in salt-tolerant than salt-sensitive genotypes suggesting that it can be considered as an important parameter in screening guar genotypes for salinity tolerance. Expression analyses of genes involved in sodium and chloride transport showed that salt-tolerant lines differed in component traits of the salt tolerance mechanisms; hence, combining different component traits may lead to superior salt-tolerant genotypes. Outcomes of this study will be utilized by guar breeders and geneticists in developing salt-tolerant varieties suitable for areas with marginal soils and/or low-quality saline irrigation water.

Technical Abstract: Guar (Cyamopsis tetragonoloba (L.) Taub.) is a legume crop, and gum derived from its seeds has various industrial applications. Due to its tolerance to various abiotic stresses, guar can be grown under water-deficit or high-salinity conditions. In this investigation, four diverse guar genotypes that performed at a similar level in field conditions were evaluated in a salinity experiment in the greenhouse lysimeter system. Based on the salt tolerance index (STI) for shoot biomass, root biomass, shoot length, and root length, Matador and PI 268229 were classified as salt-tolerant, and PI 340261 and PI 537281 as salt-sensitive. Leaf Na concentrations were 4- to 5.5-fold higher, and leaf Cl concentrations were 1.6- to 1.9-fold higher in salt-sensitive lines than salt-tolerant lines under salinity. The strong associations between the leaf K concentrations under salinity compared to the control (K-salinity/K-control) ratio and STI for stem and root length advocate higher importance of K-salinity/K-control than total leaf K concentrations. The expression analyses of genes involved in Na+ and Cl- transport revealed the importance of different component traits of salinity tolerance mechanisms, such as the exclusion of Na+/Cl- from the root, sequestration of Cl- in root vacuoles, retrieval of Na+/Cl- from xylem during salinity stress, root-to-shoot Na+/Cl- translocation, and K+-Na+ homeostasis.