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ARS Home » Pacific West Area » Logan, Utah » Forage and Range Research » Research » Publications at this Location » Publication #317602

Research Project: Develop Improved Plant Genetic Resources to Enhance Pasture and Rangeland Productivity in the Semiarid Regions of the Western U.S.

Location: Forage and Range Research

Title: Physiological processes associated with salinity tolerance in an alfalfa half-sib family

Author
item ANOWER, M - South Dakota State University
item Peel, Michael
item Mott, Ivan
item WU, YAJUN - South Dakota State University

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soil salinity is a serious global issue that threatens crop production and persistence. Alfalfa is a major forage crop worldwide, including regions of the United States that have saline soils and is sensitive to soil salinity. We previously reported the selection of two alfalfa populations with improved survival in saline growth conditions. We have further characterized the physiological mechanisms that plants from one of these half-sib families (HS-B) utilize to cope with increased salt, compared to the parent line (P-B) from which it was selected. The selected plants (HS-B) develop root structures that are 90% larger than P-B plants, and produce 86% more above ground biomass when under salt stress. Accumulation of soluble sugars is one mechanism that plants utilize to protect against increased salts, and HS-B plants were shown to accumulate more soluble sugars in the roots than P-B plants. HS-B plants were also shown to reduce stomotal conductance, a process that helps maintain water turger pressure under salt stress. HS-B plants also contained 3-4 times less reactive oxygen species (hydrogen peroxide), a detrimental compound that accumulates in cells after stress that cause damage to the cell machinery than P-B plants. Using Na+-specific dye and microscopy, it was shown that HS-B plants accumulated much less sodium (Na+) inside root cells and xylem vessels than the P-B plants, suggesting that HS-B plants have transport mechanisms that reduce the accumulation of salt within the plant tissue. The results from this study further support the hypothesis that the selected HS-B plants have greater salt tolerance than the P-B plants, and that they do so by maintaining relative water content with accumulating soluble sugars, reducing transpiration, reducing oxidative stress, and preventing accumulation of Na+ inside cells and transport structures. HS-B germplasm can be used to develop more salt tolerant alfalfas for use on land that is marginally used to do high salinity.

Technical Abstract: We prevously reported an alfalfa (Medicago sativa L.) half-sib (HS) family, HS-B, with improved salt tolerance. In this study, we showed that HS-B produced 86 and 90% greater shoot and root dry biomass, respectively compared to P-B (parental) plants under salinity stress in the greenhouse. Under saline conditions, shoots of HS-B accumulated 115% and roots 60% more soluble sugars than their P-B counterparts. The non-saline HS-B control shoots and roots also accumulated 180 and 55% more, respectively, than P-B control plants. HS-B plants also showed a greater reduction of stomatal conductance under mild saline stress than the parental plants. HS-B shoots contained 3-4 times less reactive oxygen species (H2O2) after salt treatment compared to P-B plants. Sodium localization and distribution analysis using Na+-specific dye revealed HS-B plants accumulated 90 and 48% less Na+ inside root cells and xylem vessels compared to P-B plants. These results confirmed a greater salinity tolerance in HS-B compared to P-B. Morer important, the study provides insights into the potential mechanisms that may contribute to salt tolerance in HS-B which include maintaining relative water content (RWC) by accumulating soluble sugars while reducing transpiration, maintaining healthy status by reducing oxidative stresses, and preventing salt toxicity by reducing accumulation of Na+ inside root cells and xylem.