Regulation of Na + and K + Transport and Oxidative Stress Mitigation Reveal Differential Salt Tolerance of Two Egyptian
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Regulation of Na+ and K+ Transport and Oxidative Stress Mitigation Reveal Differential Salt Tolerance of Two Egyptian Maize (Zea mays L.) Hybrids at the Seedling Stage Mosa Sayed Rizk1 · Ahmad M. M. Mekawy2 · Dekoum V. M. Assaha3 · Sumana Chuamnakthong4 · Nagwa Ebrahim Shalaby1 · Akihiro Ueda4,5 Received: 26 June 2020 / Accepted: 31 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Maize is sensitive to salinity stress, which has adverse effects on plant growth and yield. In this study, two Egyptian white maize hybrids, single cross 131 (SC131) and single cross 132 (SC132), were exposed to 100 mM NaCl stress for 12 days in a hydroponic culture and physiological and biochemical parameters, and gene expression for some Na+ and K+ transporters were evaluated. The results revealed that the total dry weight of SC131 was greater than that of SC132. The root growth was also better for SC131 than SC132. The Na+ concentration in leaves and stems, and H2O2 were significantly lower in SC131 than in SC132, while the proline concentration was higher in the leaf of SC131 than in SC132 under salt stress. Moreover, catalase and ascorbate peroxidase activities increased with salinity in SC131 leaves compared to catalase and GR in SC132. Salt stress slightly induced the expression of ZmHKT1;5 (for Na+ exclusion) in SC132, but repressed it in SC131. On the other hand, the expression of ZmHKT2 gene (for K + exclusion) was highly induced by salt stress in SC132, but was not detected in SC131. The salt increased the expression of ZmNHX1 (for vacuolar Na+ sequestration) in SC132, but repressed it in SC131. Taken together, these results suggest that the maize hybrid SC131 is more tolerant to salinity than SC132, thanks to a more efficient leaf Na+ exclusion mechanism, that is yet to be investigated, and to a better antioxidant defense system. Thus, SC131 could constitute a new hybrid worthy of consideration in maize breeding programs for enhanced productivity on salt-affected soils. Keywords Antioxidant enzyme · Na+ exclusion · Reactive oxygen species · Salt stress · ZmHKT2
Introduction
* Akihiro Ueda akiueda@hiroshima‑u.ac.jp 1
Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
2
Department of Botany and Microbiology, Faculty of Science, Minia University, El‑Minia 61519, Egypt
3
Department of Agriculture, Higher Technical Teachers’ Training College, University of Buea, PO Box 249, Kumba, SWR, Cameroon
4
Graduate School of Biosphere Science, Hiroshima University, 1‑4‑4 Kagamiyama, Higashi‑Hiroshima, Hiroshima 739‑8528, Japan
5
Graduate School of Integrated Sciences for Life, Hiroshima University, 1‑4‑4 Kagamiyama, Higashi‑Hiroshima, Hiroshima 739‑8528, Japan
Maize (Zea mays L.) is an important cereal crop (Adhikari et al. 2016) that has many critical economic uses (AbdElgawad et al. 2016). World maize production should be doubled by 2050 to meet the consumption of an increasing population (Gondim et al. 2010), but maize pr
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