Role of phosphate-solubilizing bacteria in P-uptake and growth promotion of chickpea (Cicer arietinum L.) by dissolution of inorganic phosphate

The experiment comprised of three phases. In first phase, isolation of phosphate solubilizing bacteria (PSB) were carried out from rhizosphere, roots and nodules of chickpea. The isolates were grown and purified in petri plates containing pikovskaia medium. It was observed that PSB strains isolated from chickpea (CPs-1, CPs-2 and CPs-3) were obtained only 5% of the total (50-80) bacterial colonies observed from chickpea root rhizosphere samples. No PSB strain was found in root and nodule samples of chickpea. Nine bacteria isolates, CPs-1. CPs-2, CFs-3 (isolated in the experiment), LPs- 3, WPs-S, Ca-18, AP, IFA1, IFA2 (obtained from NlBGE culture collection) were characterized by (a) Gram staining, (b) zone diameter measurement; (c) IAA production and (d) ARA activity. All PSB strains were Gram negative, rod shaped, motile, fast grower and varied in IAA production and A RA activity. Zone diameter of PSB isolates. In second phase, spectrophotometric quantification of solubilized (P) by phosphate solubilizing bacterial strains was carried out by phosphor-molybdate method. Available phosphorus soliibilized by PSB strains ranged from 65-130.5 mug ml-1. Highest valise of phosphate (130.5 mug/ml) was solubilized by, PSB strain WPs-5 followed by GPs-3 strain (103,3 mug/ml). The lowest value of phosphate (65.3 mug/ml) was solubilzed by AF strain. In third phase, effect of these PSB strains on chickpea plants way determined by a pot trial. The experiment consisted of thirteen treatments with three replicates. Out of thirteen treatments, four were without inoculation (T1, T2, T3, T4) and seven treatments (T5, T6, T7, T8, T9, T10, T11 were inoculated with PSB strains i.e. CPs-1, CPs-2, CPs-3, LPs-3, WPs-5 Ca-18 and AP respectively, while treatments T12 and T13 were inoculated with non-PSB i.e. strains IFA1, IFA2 respectively. The morpho- physiological traits were evaluated periodically along with the plant growth. The results revealed that applied PSB strains considerably enhanced seedling emergence, establishment and phosphate availability to plants. and consequently promoted plant growth chickpea plants. Favourable effect of PSB inoculation on iron accumulation is important feature of this study causing an improvement in growth and yield of plants. PSB inoculation caused an extensive increase in concentration of total nitrogen (N), nitrogenase activity, total phosphorus (P) and other cations such as Na+, K+ and Ca+2. Phosphate solubilizing bacterial strains CPs-2, CPs 3 and Ca-18 had maximum positive effect on shoot length, shoot dry weight, root area and number size and ARA activity of nodules of chickpea plants. Highest nodulation was recorded by plants inoculated with CPs-2 strain. Treatments inoculated with non PSB strains IFA1, IFA2 showed minimum values in all the parameters except root. Improved growth traits identified in the experiment; were vigorous growth of seedling, sustained photosynthetic area, better branching behaviour, more production of green tissues and high nodulation potential. A combination of these characters may be used for improving P-deficiency in chickpea plants by PSB inoculation. Conclusively, there is a great scope for improving P-deficiency in crop plants, if the criteria of PSB inoculation are incorporated in the high yielding germplasm through conventional breeding and biotechnological techniques.