Restructuring the Cellular Responses: Connecting Microbial Intervention With Ecological Fitness and Adaptiveness to the Maize (Zea mays L.) Grown in Saline–Sodic Soil

Abstract

Salt stress hampers plant growth and development. It is now becoming one of the most important threats to agricultural productivity. Rhizosphere microorganisms play key roles in modulating cellular responses and enable plant tolerant to salt stress, but the detailed mechanisms of how this occurs need in-depth investigation. The present study elucidated that the microbe-mediated restructuring of the cellular responses leads to ecological fitness and adaptiveness to the maize (Zea mays L.) grown in saline–sodic soil. In the present study, effects of seed biopriming with B. safensis MF-01, B. altitudinis MF-15, and B. velezensis MF-08 singly and in consortium on different growth parameters were recorded. Soil biochemical and enzymatic analyses were performed. The activity and gene expression of High-Affinity K+ Transporter (ZmHKT-1), Sodium/Hydrogen exchanger 1 (zmNHX1), and antioxidant enzymes (ZmAPX1.2, ZmBADH-1, ZmCAT, ZmMPK5, ZmMPK7, and ZmCPK11) were studied. The expression of genes related to lateral root development (ZmHO-1, ZmGSL-1, and ZmGSL-3) and root architecture were also carried out. Seeds bioprimed with consortium of all three strains have been shown to confer increased seed germination (23.34–26.31%) and vigor indices (vigor index I: 38.71–53.68% and vigor index II: 74.11–82.43%) as compared to untreated control plant grown in saline–sodic soil at 30 days of sowing. Results indicated that plants treated with consortium of three strains induced early production of adventitious roots (tips: 4889.29, forks: 7951.57, and crossings: 2296.45) in maize compared to plants primed with single strains and untreated control (tips: 2019.25, forks: 3021.45, and crossings: 388.36), which was further confirmed by assessing the transcript level of ZmHO-1 (7.20 folds), ZmGSL-1 (4.50 folds), and ZmGSL-3 (12.00 folds) genes using the qPCR approach. The uptake and translocation of Na+, K+, and Ca2+ significantly varied in the plants treated with bioagents alone or in consortium. qRT-PCR analysis also revealed that the ZmHKT-1 and zmNHX1 expression levels varied significantly in the maize root upon inoculation and showed a 6- to 11-fold increase in the plants bioprimed with all the three strains in combination. Further, the activity and gene expression levels of antioxidant enzymes were significantly higher in the leaves of maize subjected seed biopriming with bioagents individually or in combination (3.50- to 12.00-fold). Our research indicated that ZmHKT-1 and zmNHX1 expression could effectively enhance salt tolerance by maintaining an optimal Na+/K+ balance and increasing the antioxidant activity that keeps reactive oxygen species at a low accumulation level. Interestingly, up-regulation of ZmHKT-1, NHX1, ZmHO-1, ZmGSL-1, and ZmGSL-3 and genes encoding antioxidants regulates the cellular responses that could effectively enhance the adaptiveness and ultimately leads to better plant growth and grain production in the maize crop grown in saline–sodic soil.

Salt-Tolerant Compatible Microbial Inoculants Modulate Physio-Biochemical Responses Enhance Plant Growth, Zn Biofortification and Yield of Wheat Grown in Saline-Sodic Soil

“…Soil salinity and sodicity have become important factors that reduce the availability of cultivable land affecting agricultural production worldwide and together, are predicted to become a larger part of the problem in the times to come [ 3 , 38 ]. Globally, soil salinization reduces the available arable land in terms of the gross cropped area by 1–2% annually in the arid and semi-arid regions [ 61 ].…”

“…The findings of the present study established that, under salt stress conditions, germination percent and vigour indices of wheat increased following the treatment with bioagents as compared to the untreated control. Extensive research has been conducted to demonstrate the beneficial effects of salt-tolerant plant growth promoting microorganisms (PGPMs) on plant growth [ 29 , 37 , 38 , 65 , 66 , 67 , 68 ]. Plants challenged with high salt stress tend to overproduce and accumulate biomolecules/organic solutes and other high molecular weight compounds (osmolytes and compatible organic solutes) in their tissues to combat stress [ 28 , 69 , 70 ].…”

“…Effect of microbial inoculants on seed germination (%), vigour index I and vigour index II were assayed as per the methods suggested by International Seed Testing Association [ 48 ] with slight modifications [ 49 ]. In brief, seeds were surface-sterilized using sodium hypochlorite (NaOCl) according to Singh et al [ 38 ]. The surface sterilized wheat seeds ( cv.…”

“…Experimental evidence suggested that STRM promotes plant growth through regulation of osmotic balance, altering root size and morphology, enhancing nutrient uptake and translocation favourably [ 28 , 31 ]. In addition, certain plant growth-promoting rhizobacteria (PGPR) ameliorate ion-induced damage and improve plant growth through HKT1 (high-affinity K + transporter) gene expression in several crop plants under high salt conditions [ 29 , 34 , 35 , 36 , 37 , 38 ]. Few reports indicate that PGPR triggers localized and systemic cellular mechanisms/cascades in plants to protect them from high salt [ 38 ].…”

“…In addition, certain plant growth-promoting rhizobacteria (PGPR) ameliorate ion-induced damage and improve plant growth through HKT1 (high-affinity K + transporter) gene expression in several crop plants under high salt conditions [ 29 , 34 , 35 , 36 , 37 , 38 ]. Few reports indicate that PGPR triggers localized and systemic cellular mechanisms/cascades in plants to protect them from high salt [ 38 ]. However, the regulatory mechanisms remain unexplained [ 34 , 39 ].…”