Isolation and characterization of phosphate solubilizing rhizobacteria to improve plant health of tomato

Abstract

In the present study, 43 isolates of Phosphate solubilizing rhizobacteria (PSRB) were isolated from 37 rhizospheric soil samples of tomato collected from tomato growing regions of Karnataka. Among the 43 isolates, 33 were found to be positive for solubilizing both inorganic and organic forms of phosphorous. The isolates were analyzed for their ability to colonize roots of tomato and to increase the seed quality parameters under laboratory conditions. On the basis of above criteria, 16 isolates were selected for further studies. Organic acids from PSRB isolates were analyzed and phytase zymogram for two isolates viz., PSRB21 and 31 was prepared. Under greenhouse conditions, all selected isolates showed increased shoot length, root length, fresh weight, dry weight and phosphorous content of tomato seedlings to various extent with respect to control. Analysis of pH and available phosphorous in rhizosphere soil samples of 30 dayold-seedlings revealed that the available phosphorous content was high in rhizospheric soil samples of plants raised from seeds bacterized with PSRB isolates over control. Even though all selected PSRB's were able to increase the plant growth, only few of them showed protection against fusarium wilt and none of them against early blight.

Bio-suppression of Sclerotinia Stem Rot of Tomato and Biostimulation of Plant Growth Using Tomato-associated Rhizobacteria

“…Furthermore, excessive application of chemical fertilizers and pesticides has lead to health and environmental problems. Thus, searching for alternative control strategies that can ensure competitive yields while protecting human, plant and soil health are increasingly required [35].…”

Phosphate solubilizing bacteria: Assessment of their effect on growth promotion and phosphorous uptake of mung bean (Vigna radiata [L.] R. Wilczek)

“…Increased growth and P uptake of several crop plants due to PSB inoculation have been reported in a number of studies conducted under both growth chamber and greenhouse conditions (Dey et al, 2004;Fernández et al, 2007;Vikram and Hamzehzarghani, 2008;Hariprasad and Niranjana, 2009;Yu et al, 2011). The increase in shoot length, root length, shoot dry weight, and root dry weight of mung bean plants inoculated with PSB strains could be attributed to a greater absorption of nutrients, especially P. Compared with single inoculation, co-inoculation showed higher growth performances and P uptake; this suggests that both strains acted synergistically with each other to promote mung bean plant growth.…”

“…Phosphate solubilization potential has been attributed to the strains' ability to reduce pH of the surroundings, either by releasing organic acids or protons (Hariprasad and Niranjana, 2009). Organic acids, such as gluconic acid, oxalic acid, and citric acid, secreted by PSB can directly solubilize mineral phosphate as a result of anion exchange or indirectly chelate both Fe and Al ions associated with phosphate.…”

“…Screening of potential phosphate solubilizing isolates, which can be used as bio-inoculants to increase plant growth and yield, is recognized as an area of interest because such microbial inoculants could substantially reduce the chemical fertilizer requirement. There are several previous reports dealing with the application of phosphate solubilizing bacteria (PSB), either individually or combined, to assess their effects on the growth and biomass production of several crops (Fernández et al, 2007;Mittal et al, 2008;Vikram and Hamzehzarghani, 2008;Hariprasad and Niranjana, 2009;Jain et al, 2010). In the present study, we isolated and identified PSB strains and assessed their effect on the growth and nutrient uptake of mung bean plants cultivated under greenhouse conditions.…”

CARACTERIZACIÓN Y SELECCIÓN DE RIZOBACTERIAS PROMOTORAS DE CRECIMIENTO EN PLÁNTULAS DE CHILE POBLANO (Capsicum annuum L.)

“…Las rizobacterias poseen varios mecanismos para promover el crecimiento de las plantas, entre los que se incluye un aumento de la movilización de nutrimentos, fijación de nitrógeno, mejoramiento en la absorción de nutrientes y control biológico de patógenos (Bais et al 2006, De-Bashan et al 2007, Dias et al 2009, Hariprasad y Niranjana 2009, Altomare y Tringovska 2011. Además, sintetizan sustancias reguladoras del crecimiento como giberelinas, citoquininas y auxinas y estimulan la densidad y longitud de pelos radicales, con lo que incrementan la capacidad de absorción de agua y nutrientes, que resulta en mayor crecimiento y adaptación a condiciones de sequía, acidez y alcalinidad (Sandhya et al 2010, Saraf et al 2011).…”