Abstract
In the pursuit of sustainable agriculture through environment and human health friendly practices, we evaluated the potential of a novel gibberellins (GAs) producing basidiomycetous endophytic fungus Porostereum spadiceum AGH786, for alleviating salt stress and promoting health benefits of soybean. Soybean seedlings exposed to different levels of NaCl stress (70 and 140 mM) under greenhouse conditions, were inoculated with the AGH786 strain. Levels of phytohormones including GAs, JA and ABA, and isoflavones were compared in control and the inoculated seedlings to understand the mechanism through which the stress is alleviated. Gibberellins producing endophytic fungi have been vital for promoting plant growth under normal and stress conditions. We report P. spadiceum AGH786 as the ever first GAs producing basidiomycetous fungus capable of producing six types of GAs. In comparison to the so for most efficient GAs producing Gibberella fujikuroi, AGH786 produced significantly higher amount of the bioactive GA3. Salt-stressed phenotype of soybean seedlings was characterized by low content of GAs and high amount of ABA and JA with reduced shoot length, biomass, leaf area, chlorophyll contents, and rate of photosynthesis. Mitigation of salt stress by AGH786 was always accompanied by high GAs, and low ABA and JA, suggesting that this endophytic fungus reduces the effect of salinity by modulating endogenous phytohormones of the seedlings. Additionally, this strain also enhanced the endogenous level of two isoflavones including daidzen and genistein in soybean seedlings under normal as well as salt stress conditions as compared to their respective controls. P. spadiceum AGH786 boosted the NaCl stress tolerance and growth in soybean, by modulating seedlings endogenous phytohormones and isoflavones suggesting a valuable contribution of this potent fungal biofertilizer in sustainable agriculture in salt affected soils.
Highlights
Plant–microbe interactions are among the vital processes that are essential for the survival of both the partners and important in functioning of agricultural system
Washed roots of 10 soybean plants were cut to obtained 10 segments (0.5 cm) per plant making a total of 100 root segments which were surface sterilized in perchloric acid (Khan et al, 2008)
Assay on Waito-c rice showed that 34 strains were able to promote the growth attributes of soybean and eight strains were inhibitors
Summary
Plant–microbe interactions are among the vital processes that are essential for the survival of both the partners and important in functioning of agricultural system. Much of the attention has been focused on phytostimulation under environmental stress by these organisms in order to devise the most suitable biofertilizers (Baltruschat et al, 2008; Miransari, 2011) Plants hosting such beneficial fungi undergo significant changes in their key physiological aspects, including phytohormones balance, root exudation, composition of mineral nutrients, and physical modification in soil (Richardson, 2009; Kusari et al, 2013). An important stress among abiotic stresses is salinity, as it is responsible for diverting plant metabolism to deposit organic solutes so as to maintain turgor pressure Such osmolytes including proline have been shown to function as osmoprotectants (Munns and Tester, 2008). Fungal endophytes may be of special significance because of their ability to colonize legumes and help their partner to survive under extreme environmental conditions by secreting beneficial secondary metabolites
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