Abstract: 【Aim】 This study aims to explore the systematic defense mechanism of bean (Phaseolus vulgaris) plant against different insect pests. 【Methods】 Central leaves of each plant of P. vulgaris were fed by Spodoptera litura, Tetranychus urticae, Frankliniella occidentalis, or pricked manually with an insect needle for 6, 24, 48, 72 and 96 h, respectively, while the upper and lower leaves of each plant were left untreated. The changes in the activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) in the upper, central and lower leaves were determined. 【Results】 In the central leaves fed by the three insect species, the activities of POD, CAT and SOD changed significantly, and their changing trends varied with insect species. Compared with the control, the POD activity in central leaves fed by the three insect species increased firstly and then decreased to the level of the control after insect infestation. The POD activity reached the maximum at 24 h after T. urticae infestation, which was 4.6 times as high as the control. However, the POD activity in the central leaves increased obviously and reached the peak at 48 h after both mechanical damage and F. occidentalis infestation. The POD activity in the central leaves ingested by S. litura displayed a slowly increasing trend, and reached the maximum at 72 h after infestation. The changing trends of the CAT activity were different among mechanical damage and feeding of the three insect species. Mechanical damage induced the CAT activity obviously at 24 h after treatment, while all three insect pests caused changes of the CAT activity at earlier time, which rose significantly at 6 h and then changed in different modes with feeding time. In the central leaves, the SOD activity increased significantly only at 96 h after mechanical damage, while T. urticae infestation obviously induced the SOD activity after 24 h. Moreover, the SOD activities were significantly inhibited at 72 h in the leaves fed by S. litura or F. occidentalis. In the undamaged upper and lower leaves, the activities of POD, CAT and SOD also changed significantly after insect infestation or mechanical damage. The POD activities in undamaged upper leaves were inhibited at 96 h. However, the POD activities in lower leaves were induced to different levels. In both upper and lower undamaged leaves, the CAT activities were activated obviously at 24, 6, 6, and 24 h after mechanical damage, the infestation of S. litura, T. urticae and F. occidentalis, respectively. Mechanical damage, and S. litura and T. urticae infestation resulted in prominent increase in the SOD activity in undamaged upper and lower leaves at 96, 72 and 72 h, but F. occidentalis infestation led to the SOD activity being inhibited obviously at 48 and 72 h. 【Conclusion】 Infestation of S. litura, T. urticae and F. occidentalis can induce the activities of defensive enzymes (POD, CAT and SOD) significantly in both damaged central leaves and undamaged upper and lower leaves, which leads to systematic defensive reactions in bean plant, but the changing trends of the enzyme activities vary among treatments. These results indicate that the temporal and spatial effects of the defense are related to the species of insect pests.

Key words: Spodoptera litura, Tetranychus urticae, Frankliniella occidentalis, defensive reaction, temporal and spatial effect, enzyme activity