Abstract
Salinity causes disturbance in symbiotic performance of plants, and increases susceptibility of plants to soil-borne pathogens. Endophytic bacteria are an essential determinant of cross-tolerance to biotic and abiotic stresses in plants. The aim of this study was to isolate non–rhizobial endophytic bacteria from the root nodules of chickpea (Cicer arietinum L.), and to assess their ability to improve plant growth and symbiotic performance, and to control root rot in chickpea under saline soil conditions. A total of 40 bacterial isolates from internal root tissues of chickpea grown in salinated soil were isolated. Four bacterial isolates, namely Bacillus cereus NUU1, Achromobacter xylosoxidans NUU2, Bacillus thuringiensis NUU3, and Bacillus subtilis NUU4 colonizing root tissue demonstrated plant beneficial traits and/or antagonistic activity against F. solani and thus were characterized in more detail. The strain B. subtilis NUU4 proved significant plant growth promotion capabilities, improved symbiotic performance of host plant with rhizobia, and promoted yield under saline soil as compared to untreated control plants under field conditions. A combined inoculation of chickpea with M. ciceri IC53 and B. subtilis NUU4 decreased H2O2 concentrations and increased proline contents compared to the un-inoculated plants indicating an alleviation of adverse effects of salt stress. Furthermore, the bacterial isolate was capable to reduce the infection rate of root rot in chickpea caused by F. solani. This is the first report of F. solani causing root rot of chickpea in a salinated soil of Uzbekistan. Our findings demonstrated that the endophytic B. subtilis strain NUU4 provides high potentials as a stimulator for plant growth and as biological control agent of chickpea root rot under saline soil conditions. These multiple relationships could provide promising practical approaches to increase the productivity of legumes under salt stress.
Highlights
Legumes are highly important crops in human and animal nutrition and are grown globally under a wide range of agroclimatic conditions as a cash crop and as a source of nitrogen assimilation via nitrogen fixation (Lüscher et al, 2011; Nyfeler et al, 2011)
Numerous studies have shown that the symbiotic relationship between legumes and their rhizobia are susceptible to abiotic factors such as salinity, drought, and soil temperature, which can cause a failure in the infection and nodulation process (Slattery et al, 2001; Bouhmouch et al, 2005)
The susceptibility of plants to infection by soil borne pathogens was increased by salt stress, e.g., tomato root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici (Triky-Dotan et al, 2005), and cucumber root rot caused by Fusarium solani (Egamberdieva et al, 2011)
Summary
Legumes are highly important crops in human and animal nutrition and are grown globally under a wide range of agroclimatic conditions as a cash crop and as a source of nitrogen assimilation via nitrogen fixation (Lüscher et al, 2011; Nyfeler et al, 2011). Legumes form important symbiotic relationships with rhizobia and are known as the most efficient system for biological nitrogen fixation (BNF) (Molla et al, 2001; Egamberdieva et al, 2013, 2016a; Santi et al, 2013). Numerous studies have shown that the symbiotic relationship between legumes and their rhizobia are susceptible to abiotic factors such as salinity, drought, and soil temperature, which can cause a failure in the infection and nodulation process (Slattery et al, 2001; Bouhmouch et al, 2005). Salt stress inhibits plant growth, nutrient uptake, and increases susceptibility of plants to soilborne pathogens (Egamberdieva et al, 2011; Ahmad et al, 2015; Hashem et al, 2016). The susceptibility of plants to infection by soil borne pathogens was increased by salt stress, e.g., tomato root rot caused by Fusarium oxysporum f. Microbes associated with a plant can have beneficial interactions, providing its partner organism biologically active compounds necessary for survival and proliferation (Marschner et al, 2001; Mercado-Blanco et al, 2004)
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