Brassica Juncea Case Study

Cadmium resistant Pseudomonas sp. G1 worked as plant growth promoting bacterium that has stimulatory effects on root length of mustard seedling under cadmium stress than control. This strain has multiple plant growth properties in normal as well as cadmium contaminated environment. This strain also has co-resistance property with high MAR (multiple antibiotic resistant) value. This strain was isolated from soil of industrial area to assess its plant growth promotion and cadmium uptake in Brassica juncea. The strain G1 tolerated concentrations up to 2000 mg Cd L-1 on a nutrient agar medium. The strain G1 was characterized as Pseudomonas sps based on its 16S rDNA sequence homology because this strain not shown much similarity with already submitted

Kumar et al., reported that plants belongs to Brassicaceae family are commonly used accumulators and hyperaccumulator plants. But most of the plants belongs to this family have slow growth rate and low biomass production. Among all the plant Brassica juncea is one of the best plants which are used in phytoremediation with higher growth rate (Kumar et al., 1995; Saxena et al., 1999). Therefore PGPR assisted phytoremediation by using hyperaccumulator plants Brassica juncea is an emergent technology and need special attention to explore this area. Our aim of this study was to isolate and characterize cadmium tolerant PGPR and check their effects on growth and uptake metal of Brassica juncea in cadmium contaminated soil. Therefore, present study was divided into five main steps: i-Collection of various industrial soil, ii-Isolation and characterization of highly cadmium resistant isolates, iii- In vitro analysis to check the plant growth characteristics of selected isolates in different concentration of cadmium (0-100 ppm), iv-Treatment of mustard plant with selected cadmium tolerating PGPR and their consortia, v- Cadmium remediation and plant growth

For the 16s rDNA analysis genomic DNA was extracted and amplified in PCR using genomic DNA as template with universal primers 27F and 1492 R (Bayers et al., 1998). The PCR mixture is 25 µl contained 1 µl template, 2.5 µl of taq DNA polymerase buffer, 5mM MgCl2, 1 µl of dNTP at 2.5 mM, 0.5 µl of 2.5 unit Taq DNA polymerase 3.75 pmol primers (each) and 0.5 µl of 2.5 unit Taq DNA polymerase. The PCR was performed at 940C for 0.5 minutes, 540C for 0.5 min and 720C for 15 min followed by final extention at 72 0C for 5 minutes. Sequencing was performed by Aakaar Biotech Pvt Ltd. Lucknow, India. The obtained 16s rDNA sequence was compared with GEnebank database with the help of BLAST program (Altschul et al., 1997). The 16s rDNA sequence of strain G1 has been submitted in NCBI and the accession no. is K9.

MIC of cadmium of the Isolate G1:

MIC test was performed by using plate dilution method (Summer and Silver, 1972; Aleem et al., 2003). The minimum concentration which prevents the bacterial growth was termed as MIC. To determine the cadmium resistance bacterial cultures were inoculated into nutrient broth amended with 0, 50, 100 ppm of cadmium nitrate and incubated at 280C in 100 rpm shaking for 48 hrs. Growth analysis of isolates was done by measuring OD at 600nm.

Evaluation of PGP