Induction Of Systemic Resistance In Tomato Plants To Gray Mould (Botrytis Cinerea) By Antagonistic Bacteria And Mechanisms Involved In Induced Resistance

Induced systemic resistance (ISR) in tomato plants to gray mould (Botrytis cinerea) by Bacillus licheniformist W10, Paneibacillus polymyxa W3 and Y2, and their bacteria-free suspension (BFS) and the mechanisms of induced resistance were studied in this paper.Systemic resistance was induced to gray mould when tomato leaves were treated with antagonistic bacteria and their BFS. The strain W3 and its BFS were found to be the most effective in the induction of systemic resistance among 3 strains of the bacteria. Their induction effects were 64.5% and 53.1% respectively. When the plants were treated with W3 and its BFS, the induced resistance occurred at the third day and reached the top at the fifth day after the treatment. Then it decreased gradually and lasted to the twelfth day. There was significant difference in induction effects among the different concentrations of the bacterium used. The induced resistance was enhanced with the increment of bacterial concentration. The induced resistance was the maximum when bacterium was 108cfu/ml. The resistance was induced in different leaves above the leaves treated with the bacterium and its BFS, but there was no significant difference in induced resistance among different leaves.After inducing inoculation of W3 and its BFS, the activity of superoxide dismutase (SOD), peroxidase (POD), polypenoloxidase (PPO), phenylalam'ne ammonialyase (PAL) in tomato leaves was obviously increased. The activity of POD and PPO began to rise at the first day after the treatment and reached the peak at the third day with 51.4% and 78.1% higher than that of control, and then declined gradually, but still with 20% and 47.4% higher than that of control at the sixch day. SOD activity started to rise apparentlyat the first day and reached the maximum at the second day, with 52.42 unit enzyme activity higher than that of control. Then it declined gradually and was nearly as much as that of control at the sixth day. PAL activity reached the peak at the first day after treatment, with 3.9 times that of control, and then it declined gradually, but still with 2.5 times that of control at the sixth day. Although the activity of defendant enzymes mentioned above could be improved in tomato plants after inoculation of the pathogen, the enzyme activity induced by the antagonistic bacterium and its BFS arise more quickly and greatly, and declined slowly. Furthermore, the variations in defendant enzyme activity when tomato plants were inoculated with the antagonistic bacterium and the pathogen at the same time resembled those when they were treated only with the bacterium.Active oxygen species (AOS) in tomato leaves after the induction of W3 and its BFS was increased at the first day by 89% higher than that of control and by 155.6% higher than that after the inoculation with the pathogen, and declined quickly after the second day by 111.8% lower than that after the inoculation with the pathogen and was near to that of control at the sixth day. The variation in active oxygen production speed when tomato leaves were inoculated with the bacterium and the pathogen at the same time was similar to that when they were treated only with the bacterium.Salicylic acid (SA) in treated leaves was significantly increased after tomato plants were induced by the antagonistic bacterium. Accumulation of SA in treated leaves ascended to 2.25ng/g at the first day after treatment and descended 2 days later. But it persisted in a certain level, which was 80.5% higher than that of control. SA in the leaves above the treated leaves was also increased at the first day after treatment and peaked at the second day with 59.2% higher than that of control. It kept in above leaves 10% more than that of control even though at the third day.The experimental results showed that there was close relativity between the increment in induced resistance and the variation in defendant enzyme activity intomato plants. The peak of PAL and SOD activity came earlier than that of induced effects (at the third day) an...