Cabbage Resistance Induced By Diamondback Moth, Plutella Xyllostella And Its Effect

Plant induced resistance can be activated by herbivore infestation. Induced resistance triggers a series of physiological and biochemical changes in plants, which may adversely affect pests, and enhance plant resistance to pests, thus improving the adaptability of plants to this pest.In our research, the role of GOX as an inducer of resistance in cabbage was examined by measuring the levels of activity of GOX in DBM of different ages and in various tissues. Then, diamondback moth (Plutella xyllostella L.) and cabbage (Brassica oleracea L.) were selected to examine the effects of different inducing factors and changes in defense mechanisms of cabbage to DBM. Temporal variation of defensive protein trypsin inhibitor (TI) and defensive signal jasmonic acid (JA) in cabbage was examined using various feeding treatments such as mechanical wounding with phosphate buffer saline (PBS), mimic insect feeding with regurgitate, Aspergillus niger glucose oxidase (GOX) and Aspergillus niger glucose oxidase+ Glucose (GOX+GLC). We also observed diamondback moth developmental duration, pupal weight, fecundity and other indicator changes with different inducing factor treatments. The main findings were as follows:(1) Glucose oxidase (GOX) activity in DBM of different ages, DBM tissues and regurgitate showed that DBM midgut and regurgitate had the highest levels of GOX activity. The other tissues were significantly lower than the first two. The forth instar feeding actively had the highest GOX activity level, significantly higher than the second and third instars.(2) Effect of different inducing factors on cabbage trypsin inhibitor (TI) level: Insect feeding and cabbage wounding with PBS had no significant influence on TI level. The regurgitate induced a significant increase in TI level. There was no difference in GOX+GLC treatment and control. This showed that the DBM feeding and wounding with PBS would not induce defense protein-TI increase in cabbage. Cabbage could not become resistance to DBM infestation through trypsin inhibitor.(3) Effect of different inducing factors on cabbage Jasmonic acid (JA) level: After larval feeding and PBS treatment 2 h, cabbage JA was significantly increased and the level was significantly higher in PBS treatment than larval feeding. JA level showed no significant difference between the regurgitate treatment and control. The JA level of cabbage treated with PBS significantly decreased between 6-24 h, but not larval feeding. GOX and GOX+GLC treatment significantly lowered JA levels when compared with the control. We concluded that DBM feeding and PBS treatment could induce cabbage defense signals JA at different degrees and GOX might be the possible factor influencing this variation.(4) Effect of different inducing factors on DBM growth and development:DBM development duration was shortened when fed with cabbage damaged by larvae, but prolonger under PBS treatment. The other treatments had no significant difference. PBS treatment significantly reduced pupal weight, emergence rate, and fecundity. Mortality was not significantly different among treatments. These results suggested that cabbage induced resistance did not significantly affect the growth and development of the DBM.The above findings showed that the DBM feeding and wounding with PBS had no significant effect on inducing the trypsin inhibitor level change. But the level of the defense signal JA significantly increased. And glucose oxidase (GOX) may play a role in the inhibition of induced resistance of defense signals. In addition, the cabbage induced resistance cannot affect diamondback moth growth and development. The results provide a theoretical basis for illuminating the chemical interactions between the DBM and its host plant cabbage.