The Induced Resistance Of AR99 For Tomato Bacterial Wilt

AR99 is a biocontrol preparation against the disease caused by soil-borne pathogens. In our previous work, AR99 can suppress the tomato disease caused by Ralstonia solanacearum. In order to reveal the mechanism of AR99, we report here that the level of superoxide dismutase (SOD), phenylanine ammonia lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) was changed significantly when the AR99 was drenched into the rhizosphere of tomato in the greenhouse . Our result showed that the level of PAL and PPO of tomato treated with AR99 increased significantly compared to that of non-treatment control. The activity of SOD with treatment increased significantly at 12h compared to the control, while after that it declined and did not show significant difference, even lower at 48 and 72h compared to the control. Although the level of POD with treatment is a little higher compared to the control, but there is no significant difference between them. The highest level of these four enzymes with treatment turns up at different period. The level of SOD was highest at 12h, while the activity of PAL and PPO came to maximum at 72h, followed the POD at 96h.The content of reactive oxygen species (ROS) in plant is closely relative to disease resistance. The change of content of hydrogen peroxide (H2O2) and activity of catalase (CAT) and ascrobate peroxidase (APX) in AR99-treated tomato after challenged with Ralstonia solanacierum was studied in this work. The result showed that the content of H2O2 with AR99 treatment increased significantly 12h after pathogen-challenge compared to the non-induced control. But the HR was not seen throughout the work neither in AR99 treatment nor in the control. The level of CAT and APX changed in contrast to the content of H2O2, but the change was different between CAT and APX. The CAT was more relative to content of H2O2 in the initially time after pathogen-challenge, while the APX was more sensitive in the latter.Strain AR21 is a main ingredient of AR99 and can suppress the disease by Ralstonia solanacearum when drenched to the soil by oneself. In this work, a plasmid pGFP315 which carried a gfp gene was transferred into AR21, which resulted in AR21-gfp. The expression of gfp in the AR21-gfp can be detected under ultraviolet radiation or by afluorescence microscope. The strain AR21-grp showed no difference from strain AR21 in growth. Plasmid stability study indicated that the pGFP315 can be inherited very well. The study for colonization of AR21-gfp in rhizosphere indicated that the strain main colonized on the base root, and the colony on the middle root is the least.