Plant Stress (Mar 2024)
“Halotolerant fungi secreting phytohormones and volatile organic compounds enhance growth and mineral content in finger millet under salinity stress”
Abstract
Soil salinity is one of the major environmental stresses that significantly hampers crop yield worldwide. This study assessed the effectiveness of the rhizospheric fungus, Aspergillus sojae JUSPF-101, in enhancing the tolerance of finger millet seedlings to NaCl stress. The research also examined the role of JUSPF-101 in producing phytohormones and volatile organic compounds. The impact of A. sojae was evaluated on both primed and unprimed finger millet seedlings (using Petri dish and pipette tip bioassay methods) under NaCl stress conditions. A study was conducted in a greenhouse to confirm the growth characteristics and mineral composition of finger millet seedlings, both with and without inoculation of A. sojae JUSPF-101. These seedlings were exposed to varying concentrations of NaCl (0 and 400 mM).The current research demonstrated that A. sojae could withstand high concentrations of NaCl (up to 1200 mM) and high temperatures (45 °C). Using LC-MS/MS, fifteen phytohormones were identified in A. sojae grown under NaCl concentrations of 0 and 400 mM. These include IAA, SA, GA4, epibrasinolide, the trans isomer of zeatin, and cis-jasmone. The GC–MS analysis detected seventy-seven VOCs, with the major compound being 1-(4-Amino-furazan-3-yl)-5-propyl-1H-[1,2,3]triazole-4-carboxylic acid ethyl ester (8.7%). Moreover, finger millet seedlings that were not treated displayed a significant decrease in RWC and biochemical parameters such as proline, phenols, and flavonoids (p < 0.05), while there was an increase in MDA and H2O2 content. However, using A. sojae effectively alleviated the stress caused by NaCl and led to improvements in RWC, growth, and biochemical parameters.The application of A. sojae under 400 mM NaCl treatment, significantly increased morphological (shoot and root length) and biochemical parameters such as proline (1.67-fold), phenols (2.15-fold), and flavonoids (2.04-fold) while MDA (1.2-fold), and H2O2 (1.25-fold) decreased as compared to unprimed seedlings under NaCl stress. In a greenhouse environment, seedlings treated with A. sojae showed improved growth parameters and lower Na+/K+ and Na+/Ca2+ ratios. These findings suggest that applying A. sojae (JUSPF-101) could be an effective strategy for reducing NaCl stress in finger millet, contributing to sustainable food security.
