title: Characterization of physiological responses of two alfalfa half-sib families with improved salt tolerance.
abstract: Alfalfa (Medicago sativa L.) is a major forage crop worldwide that is relatively sensitive to soil salinity. Improved cultivars with high production on saline soil will benefit many producers and land managers. This study reports the characterization of physiological responses of two unrelated experimental alfalfa half-sib families, HS-A and HS-B, selected for their improved survival under saline conditions (up to EC 18). Six-week-old plants were subjected to NaCl-nutrient solution treatment for three weeks starting at an electrical conductivity (EC) of 3 dS m(-1) with incremental increases of 3 dS m(-1) every week, reaching 9 dS m(-1) in the third week. HS-B showed greater leaf number (72%) and stem length (44%) while HS-A showed better leaf production (84%) under salt treatment compared to the initial genetic backgrounds from which they were developed. This improved growth is associated with 208% and 78% greater accumulation of chlorophyll content in HS-B and HS-A, respectively. Both HS-A and HS-B also showed improved capability to maintain water content (RWC) under salt stress compared to the initial populations. Differing from its initial populations (P-B), HS-B did not accumulate Na in shoots after salt treatment. HS-B also maintained K(+)/Na(+) and Ca(2+)/Na(+) ratios, while P-B showed 59% and 69% decrease in these ion ratios, respectively. Na(+) content in HS-A was not different from its initial populations (P-A) after salt treatment. However, HS-A showed an enhanced accumulation of Ca(2+) and maintained the levels of Mg(2+) and K(+) in shoots compared to the P-A populations. This study provides physiological support of improved salt tolerance in HS-A and HS-B and suggests that these plants maintain ion homeostasis but have different mechanisms of coping with high salinity.
authors.affiliation: Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: M Rokebul
authors.initials: MR
authors.lastname: Anower
authors.forename: Ivan W
authors.initials: IW
authors.lastname: Mott
authors.forename: Michael D
authors.initials: MD
authors.lastname: Peel
authors.forename: Yajun
authors.initials: Y
authors.lastname: Wu
mesh_terms: D000455:Medicago sativa / Q000187:drug effects* / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000378:metabolism; D055049:Salt Tolerance / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D012965:Sodium Chloride
keywords: Alfalfa; CCI; Chlorophyll; HS-A; HS-B; Ion content; Leaf number; P-A; P-B; Salt tolerance; Stem length; chlorophyll content index; initial parental breeding population containing Medicago sativa ssp. sativa cultivars Malone, Mesa Sirsa and Saranac; initial parental breeding population of Medicago sativa ssp. falcata BC79; salt-tolerant falcata-type alfalfa half-sib family derived from P-B; salt-tolerant sativa-type alfalfa half-sib family derived from P-A