Abstract
Environmental pollution problems and increased demand for green technologies in production are forcing farmers to introduce agricultural practices with a lower impact on the environment. Chickpea (Cicer arietinum) in arid and semi-arid environments is frequently affected by harsh environmental stresses such as heat, drought and salinity, which limit its growth and productivity and affect biological nitrogen fixation ability of rhizobia. Climate change had further aggravated these stresses. Inoculation with appropriate stress tolerant rhizobia is necessary for an environmentally friendly and sustainable agricultural production. In this study, endophytic bacteria isolated from chickpea nodules from different soil types and regions in Morocco, were evaluated for their phenotypic and genotypic diversity in order to select the most tolerant ones for further inoculation of this crop. Phenotypic characterization of 135 endophytic bacteria from chickpea nodules showed a wide variability for tolerance to heavy metals and antibiotics, variable response to extreme temperatures, salinity, pH and water stress. 56% of isolates were able to nodulate chickpea. Numerical analysis of rep-PCR results showed that nodulating strains fell into 22 genotypes. Sequencing of 16S rRNA gene of endophytic bacteria from chickpea nodules revealed that 55% of isolated bacteria belong to Mesorhizobium genus. Based on MLSA of core genes (recA, atpD, glnII and dnaK), tasted strains were distributed into six clades and were closely related to Mesorhizobium ciceri, Mesorhizobium opportunistum, Mesorhizobium qingshengii, and Mesorhizobium plurifarium. Most of nodulating strains were belonging to a group genetically distinct from reference Mesorhizobium species. Three isolates belong to genus Burkholderia of the class β- proteobacteria, and 55 other strains belong to the class γ- proteobacteria. Some of the stress tolerant isolates have great potential for further inoculation of chickpea in the arid and semiarid environments to enhance biological nitrogen fixation and productivity in the context of climate change adaptation and mitigation.
Highlights
Chickpea (Cicer arietinum) is a socially and economically important food legume in South Asia, West Asia, North Africa and Mediterranean regions
Phylogenetic analysis of the symbiosis genes revealed that they share common symbiosis genes and similar to those carried by M. ciceri and M. mediterraneum, which suggests a lateral transfer of symbiosis genes across different species (Rivas et al, 2007; Laranjo et al, 2008)
We demonstrated that rhizobia nodulating chickpea in Morocco could be classified with M. ciceri, M. opportunistum, M. qingshengii, M. plurifarium, and other unnamed Mesorhizobium genospecies
Summary
Chickpea (Cicer arietinum) is a socially and economically important food legume in South Asia, West Asia, North Africa and Mediterranean regions. It ranks second in area and third in production after beans and pea (Muehlbauer and Sarker, 2017). Chickpea plays a major role in sustainable and environmental friendly agriculture It can establish symbiosis relation with rhizobia able to reduce atmospheric nitrogen into ammonia directly assimilated by plants, which enhances this crop’s and subsequent cereal crops productivity, improves soil fertility by fixing nitrogen at rates of up to 140 kg/ha/year (Flowers et al, 2010), reduces significantly the use of chemical fertilizers and diminishes global warming and water contamination (De la Peña and Pueyo, 2012). Detailed studies on species nodulating chickpea in Morocco are lacking
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