Sodium exclusion by different maize genotypes under salinity in conferring salt resistance

An experiment was carried out in the pot-house of botanical garden of Bangladesh Agricultural University (BAU), Mymensingh, during June to November, 2014 to investigate the effect of NaCl on growth, Na+ accumulation and K+: Na+ ratio in maize. Four maize genotypes namely BARI Maize 5, BARI Maize 7, Plain maize line and Mosaic maize line were tested against control, without providing any NaCl and salt stress, with NaCl to reach the soil salinity of 10 dS m-1. The experiment was laid out following CRD with four replicates. Under salt stress, relative reduction in shoot fresh masses were 22 and 77% in BARI Maize 5 and BARI Maize 7, whereas the magnitude of reduction was 136 and 155% in Mosaic maize line and Plain maize line, respectively. Seven days exposure to moderate salinity (10 dS m-1) seemed to have significantly reduced total fresh masses with the concomitant increase in Na+ concentrations but decrease in K+ concentrations and K+: Na+ ratios in both young and old shoots of BARI Maize 5, Plain maize line and Mosaic maize line. In contrast, BARI Maize 7 showed significant reduction in shoot fresh mass under salinity with the concomitant increase in shoot Na+ content but no significant changes in K+ concentrations and K+: Na+ ratios were observed under salinity. It seemed that young leaf of BARI maize 7 showed unaffected growth despite of higher accumulation of Na+. It may likely that BARI maize 7 sequestered incoming excess Na+ ions in the vacuole from the cytosol to combat deleterious effect of this ion to the cytoplasmic enzymes.Asian J. Med. Biol. Res. December 2016, 2(4): 562-566

Impact of ancestral wheat sodium exclusion genes Nax1 and Nax2 on grain yield of durum wheat on saline soils

Nax1 and Nax2 are two genetic loci that control the removal of Na+ from the xylem and thereby help to exclude Na+ from leaves of plants in saline soil. They originate in the wheat ancestral relative Triticum monococcum L. and are not present in modern durum or bread wheat. The Nax1 and Nax2 loci carry TmHKT1;4-A2 and TmHKT1;5-A, respectively, which are the candidate genes for these functions. This paper describes the development of near-isogenic breeding lines suitable for assessing the impact of the Nax loci and their performance in controlled environment and fields of varying salinity. In young plants grown in 150 mM NaCl, Nax1 reduced the leaf Na+ concentration by 3-fold, Nax2 by 2-fold and both Nax1 and Nax2 together by 4-fold. In 250 mM NaCl, Nax1 promoted leaf longevity and greater photosynthesis and stomatal conductance. In the uppermost leaf, the Na+-excluding effect of the Nax loci was much stronger. In the field, Na+ in the flag leaf was reduced 100-fold by Nax1 and 4-fold by Nax2; however, Nax1 lines yielded 5–10% less than recurrent parent (cv. Tamaroi) in saline soil. In contrast, Nax2 lines had no yield penalty and at high salinity they yielded close to 25% more than Tamaroi, indicating this material is suitable for breeding commercial durum wheat with improved yield on saline soils.