Biological characteristics of quinclorac-degrading Stenotrophomonas maltophilia strain J03 and its safety evaluation on tobacco and rice

Quinclorac has been widely used in rice for the control of weeds. However, its residue in rice-tobacco rotation field is detrimental for tobacco growth. Our previous studies revealed that Stenotrophomonas maltophilia strain J03 isolated from a tobacco field in Fujian province had a great ability for the remediation of quinclorac damage to tobacco. To explore the safety risk of J03 to the growth of tobacco and rice and its characteristics, the effect of J03 on seed germination and seedling growth, and the effect of temperature and pH on J03 growth were investigated. The results showed that the seed germination rates of tobacco and rice after J03 treatment was greater than 80% and 95% respectively, which have no significant difference with those of their control groups. The tobacco treated by J03 has 2.82 cm seedling height, 6.4 leaves and 6.08 g above-ground fresh weight, which were greater than those of the CK. Moreover, there was no significant difference on other traits between tobacco treated by J03 and the control. After treated by J03, the rice seedling height and leaf area have no significant difference with those of the CK either. J03 survived in the temperature ranged from 4 ℃ to 40 ℃ with the optimum range of 30 ℃ to 40 ℃. It grew well in LB cultural medium with pH values from 5.0 to 9.0 with the optimum range of 6.0 to 8.0. In summary, the S. maltophilia J03 is safe for the growth of tobacco and rice with strong potential adaptaion in field.