The Physiological And Biochemical Effects And The Induced Defense Responses Of Tobacco Infested By B-Biotype Bemisia Tabaci(Gennadius)

The invasive B-biotype Bemisia tabaci infest many economic crop plants in China.They have been widespread in most tobacco fields in Shandong province, and brought severe damage in some areas. There are competitive advantages when they compete with the indigenous insects. In this paper, we investigated the effects of the B-biotype Bemisia tabaci infestation on the tobacco growth, physiological and biochemical indices to discuss the role of the B-biotype Bemisia tabaci feeding on tobacco-induced defense response in the B-biotype Bemisia tabaci competing with the indigenous insects. The main results are as follows:1. The effects of the B-biotype Bemisia tabaci infestation on the growth of tobacco: when the nymphs infested tobacco to the 3rd instar, the vein of the tobacco leaves became white. The plant height and the space of the nodes of tobacco infested by the B-biotype Bemisia tabaci were inhibited. However, the length and veins width of the main functional leaves did not change significantly. The chlorophyll content decreased 36.62%-67.92%, and the net photosynthetic rate (Pn) declined significantly.2. The effects of B-biotype Bemisia tabaci infestation on the reactive oxygen species metabolism in tobacco: superoxide anion (O2-) production rate is different in different positions tobacco leaves of tobacco infested by B-biotype Bemisia tabaci. Compared with the control, superoxide anion production rate in the damage leaves increased significantly, about 2.44 times, while in white- vein leaf blade it reduced compared with its control. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) in white-vein leaves increased significantly, rising by 0.4 times, 3.15 times, 12.5 times, respectively. However, the activities of the three enzymes were lower than their control in the damage leaves.3. The effects of B-biotype Bemisia tabaci infestation on the peroxidase (POD) and polyphenol oxidase (PPO) activity in tobacco: The infestation of the B-biotype Bemisia tabaci induced the increase of POD activities in different tobacco leaves compared with their control, and the activity in white-vein leaves increased more than the damage leaves. The PPO activity in the white-vein leaves increased significantly, rising by 83.49%. These two anti-nutritional enzymes play an important role in the resistance to insects.4. The effects of B-biotype Bemisia tabaci infestation on the phenols in tobacco: The B-biotype Bemisia tabaci infestation increased the total phenols content in different tobacco leaves. Compared with the control, the total phenols content in damage leaves increased 62.29%. The Phenolic metabolism enzyme phenylalanine ammonia-lyase (PAL) activity in different positions leaves increased, and the activity in damage leaves increased largest. POD, PPO can oxidize the phenols into more toxic products to prevent insects from feeding.