Abstract
Chickpea is one of the major legume crops widely grown in Ethiopia. The low availability of phosphorus in soil is among the stresses that constrain the production of this crop in the country. However, there are rhizobacteria capable of solubilizing insoluble forms of phosphorus in soil and make it available to the plant. Thus, this study was aimed at isolation and characterization of phosphate solubilizing bacteria from chickpea rhizosphere. Fifty phosphate solubilizing bacterial strains were isolated from the soil samples, characterized biochemically and identified by 16S rDNA sequences analysis. The results indicate the presence of genera Acinetobacter, Bacillus, Brevibacillus, Burkholderia, Empedobacter, Enterobacter, Pseudomonas, Ralstonia, Sphingomonas and Stenotrophomonas. Phosphate solubilizing efficiencies of the strains were analyzed using different insoluble phosphorus sources and the results show that most isolates released a substantial amount of soluble phosphate from tricalcium phosphate, rock phosphate and bone meal. Screening for multiple plant growth promoting attributes showed that 44 and 18% of them were capable of producing indole acetic acid and inhibiting the growth of Fusarium oxysporum under in vitro conditions, respectively. A direct impact of several strains (Bacillus flexus (PSBC17), Pseudomonas fluorescence (PSBC33), Enterobacter sp. (PSBC35), Enterobacter sakazaki (PSBC79) and Enterobacter sp. (PSBC81)) on the growth of chickpea in pot culture has been demonstrated by the increase in the number of root nodules, shoot dry matter, nitrogen and phosphorus concentration of shoot. Based on the results, we conclude that chickpea rhizosphere harbor phosphate solubilizing bacteria which are diverse in taxonomy and phosphate solubilizing efficiencies. Thus, consecutive studies should focus on field studies on those strains due to their potentially high importance for the phosphorus nutrition of crops in this area and in this context for the improvement of the sustainability of crop production in the country. Key words: Plant growth promoting rhizobacteria (PGPR), indole acetic acid (IAA), rhizosphere soil, rock phosphate, bone meal.
Highlights
Chickpea (Cicer aeritinum L.) is one of the major food legume crops grown widely in tropical, sub-tropical and temperate regions of the world
The results revealed the presence of diverse groups of phosphate solubilizing bacteria in the rhizosphere of chickpea
They were dominated by Gram negative rhizobacteria which accounted for 86% of the isolates (Table 2)
Summary
Chickpea (Cicer aeritinum L.) is one of the major food legume crops grown widely in tropical, sub-tropical and temperate regions of the world. It is widely grown in Ethiopia over an area of 208,388.6 ha (Central Statistical Agency (CSA), 2011). Chickpea restores and maintains soil fertility and grown in rotation with major cereals in traditional low-input agricultural systems. This is due to its ability to fix dinitrogen in association with root nodule bacteria belonging to the genus Mesorhizobium (Nour et al, 1994). Its yield has remained rather low due to several stresses which prevail under Ethiopian edaphoclimatic conditions (Keneni et al, 2011; Jida and Assefa, 2012)
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