Abstract
Arachis hypogea (Peanut) is one of the most important crops, and it is harvested and used for food and oil production. Being a legume crop, the fixation of atmospheric nitrogen is achieved through symbiotic association. Nitrogen deficiency is one of the major constrains for loss of crop productivity. The bacterium Stenotrophomonas maltophilia is known for interactions with plants. In this study, characteristics that promote plant growth were explored for their ability to enhance the growth of peanut plants under N2 deficit condition. In the presence of S. maltophilia, it was observed that fatty acid composition of peanut plants was influenced and increased contents of omega-7 monounsaturated fatty acid and omega-6 fatty acid (γ-Linolenic acid) were detected. Plant growth was increased in plants co-cultivated with PGPR (Plant Growth Promoting Rhizobacteria) under normal and stress (nitrogen deficient) condition. Electrolyte leakage, lipid peroxidation, and H2O2 content reduced in plants, co-cultivated with PGPR under normal (grown in a media supplemented with N2 source; C+) or stress (nitrogen deficient N+) conditions compared to the corresponding control plants (i.e. not co-cultivated with PGPR; C–or N–). The growth hormone auxin, osmoprotectants (proline, total soluble sugars and total amino acids), total phenolic-compounds and total flavonoid content were enhanced in plants co-cultivated with PGPR. Additionally, antioxidant and free radical scavenging (DPPH, hydroxyl and H2O2) activities were increased in plants that were treated with PGPR under both normal and N2 deficit condition. Overall, these results indicate that plants co-cultivated with PGPR, S. maltophilia, increase plant growth, antioxidant levels, scavenging, and stress tolerance under N2 deficit condition. The beneficial use of bacterium S. maltophilia could be explored further as an efficient PGPR for growing agricultural crops under N2 deficit conditions. However, a detail agronomic study would be prerequisite to confirm its commercial role.
Highlights
Different abiotic stresses are a major problem associated with arid and semi-arid regions
The bacterium S. maltophilia was grown in nitrogen-free semisolid NFb medium with malate as a carbon source to confirm the nitrogen-fixing ability of the bacterial strain
An amplicon of expected 360 bp was obtained with degenerate nifH primers [55, 56], which confirmed the presence of the nifH gene in the bacterium (S1 Fig)
Summary
Different abiotic stresses are a major problem associated with arid and semi-arid regions. Stresses are of natural or human-induced (anthropogenic) processes that inhibit plant growth [1]. Salinization is a major constraint for the crop productivity and it has been estimated that an approximate area of 7 million hectares of land is covered by saline soil in India [2]. Salinity affects the glycophytic plants at cellular, morphological, physiological and molecular levels [3, 4]. Salt interrupts the soil nutrient balance which affects the growth of plant [5]. Halophytes have the ability to grow under high saline areas and are considered a rich source of metabolites [6, 7], oligosaccharides [8], proteins [9], genes [10,11,12,13,14,15,16,17,18,19,20,21,22], promoters [23,24,25] and renewable energy [26]
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