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Phytoremediation of petroleum and its derivatives has frequently been regarded as a practical, eco-friendly alternative to the clean-up of petroleumcontaminated soils. In this study, Vetiveria zizanioides (L.) Nash (vetiver) is shown to efficiently remediate two petroleum-contaminated soils; fresh contamination (FC) with 3500 mg kg À1 aliphatic petroleum hydrocarbons (APH), and aged contamination (AC) with 700 mg kg À1 . An 88.5% reduction in the concentration of APH is observed in both contaminated soils where vetiver are grown for 15 months. Vetiver vegetation also doubled (FC) and tripled (AC) the bioavailability of contaminants as compared with unvegetated soils, as determined by the release of APH into the soil solution. The carbon availability index increased in both vegetated soils (%1), and the microbial biomass carbon shows a three-and five-fold increase in vegetated soils FC and AC, respectively, leading to a fourfold decline in the metabolic quotient. The mRNA level of nosZ gene increased significantly in the soils under vetiver vegetation, and was correlated with the accumulation of APH in the soil solution; this probably demonstrates the role of hydrocarbon bioavailability in promoting biological processes and biodegradation. It is concluded that vetiver vegetation increased hydrocarbons bioavailability and hence raised the extent of biodegradation hydrocarbons in the soil.

Optimization of DNA extraction protocols for plant tissues and including endophytic microorganisms is a critical step of advanced plant-microbe interaction in agricultural studies. Pistachio (Pistacia vera L.) root tissue contains high levels of polyphenols have been known as major extract contaminants and inhibitors of enzymatic activities during amplification. The present study aimed to develop reliable strategies to purify DNA from Pistachio root samples. Inhibiting substances were removed from DNA through a process including extraction with hot detergent contains SDS-Tris-EDTA, AlNH 4 (SO 4 ) 2 .12H 2 O as chemical coagulating factor and CTAB-NaCl. Following typically organic extraction/alcohol precipitation, denaturing agarose electrophoresis performed to purify probable remain contaminants. The purified DNA was enough free of polyphenols based upon loss of color and spectral quality (260/230>1.6) and efficiently amplified during polymerase chain reaction particularly in the present of GC-clamp primers. This method proved well with detection of Glomus sp. (arbuscular mycorrhiza fungi) associated with Pistacia vera L. using denaturing gradient gel electrophoresis (DGGE).