One strain of microorganisms was isolated from soil previously treated with pendimethalin using enrichment technique and identified using 16S rDNA as Pseudomonas putida (E15). The effect of pH and temperature on the growth ability of the tested strain was investigated. The results show that the optimum pH and temperature for the growth of pendimethalin dissipating strain were 7 and 30°C, respectively. P. putida was used to dissipate pendimethalin from mineral liquid medium with half-live of 5.46 days. Pendimethalin half-live was 51.9 days in untreated mineral liquid medium. P. putida and compost were also evaluated for detoxification of pendimethalin in clay soil. P. putida and compost were effective in pendimethalin dissipation in soil with half-live of 4.67 and 5 days, respectively. Pendimethalin half-live was 62.43 days in untreated soil. Pendimethalin treatment affected analysis of the microbial population growing in P. putida or compost treating soil leachates showed an overall increase in the population of microorganisms. There is no toxicity of pendimethalin detected in soil on cucumber plants after treatment with P. putida or compost. Pendimethalin significantly decreased germination and increased cucumber seedlings mortality rate. P. putida and compost treatments increased the growth parameters. Moreover, no significant difference was observed in the most growth parameters between P. putida and compost treatments. Abnormal development of xylem tissue was observed in pendimethalin contaminated soil as a result of phytotoxicity. The results suggest that bioremediation by P. putida and compost was considered to be effective method for detoxification of pendimethalin in soil.
Key words: Pendimethalin, soil, biodegradation, phytotoxicity, seedling mortality.