| Tomato (Solarium lycopersicum Mill.) is one of most favorite vegetables and widely cultivated in the world. In China the tomato is largest planting area among all kinds of fruits and vegetables. Bemisia tabaci (Gennadius) is an important pest in the tomato. The adults and nymphs suck the juice of S. lycopersicum, leading to the nutrition lack, reduced growth and deformed of the plant, and the physiological activities are also affected. Therefore, yield and quality of tomato declined dramatically. Meanwhile, it transmits tomato virus disease and results in huge threat of the tomato production. B. tabaci is a worldwide invasion pest and characteristic of strong reproductive capacity, short life cycle, serious overlapping generations and easy outbreaks. Thus they are usually controlled by the chemicals. With the development of the economy, we increasingly pay attention to the quality and safety of tomato. To better improve the yield and quality of tomato and provided theory for the whitefly control, the effects mechanism of B. tabaci feeding on the growth, development and quality of S. lycopersicum, the selective mechanism of B. tabaci on the various tomato varieties, the determination of chemical control index and the application techniques of nitenpyram for control whitefly were studied. The results asfollowing:1. The effect on growth and development of the tomato by B. tabaci fed was investigated.To detect the effect on the development of tomatoes damaged by B. tabaci,the ninth leaf stage tomatoes were inoculated by To detect the effect on the development of tomatoes damaged by B. tabaci, the ninth leaf stage tomatos were inoculated by a certain number of B. tabaci. The result exhibited the growth and development of S. lycopersicum was inhibited obviously fed.by B. tabaci and the differences were significant accompanying by the increase of number of B. tabaci and feeding time. After twenty-eight days, the aerial dry weight of tomato in 50 individuals per plant (treatment 1) and an 450 individuals per plant (treatment 2) fed by B. tabaci, were 67.92% and 40% of control group respectively. B. tabaci damaged also reduced the root dry matter weight of tomato. For example, after twenty-eight days, the root dry matter weight of tomato treatment 1 and 2 ware 70.86% and 49.89% of control group respectively, and the root length of tomato in treatment 1 and 2 were 78.32% and 57.96% of control group respectively. In the all experiment, the root length of tomato fed by B. tabaci always shorter than that of control. But with the increase of number of pests, the root shoot ratio in dry weight of tomato has increased. For example, after twenty-eight days, the root shoot ratio in dry weight of tomato in treatment 1 and 2 ware increased 19.58% and 4.3% of control group respectively. And the root length of tomato in treatment 1 and 2 were 78.32% and 57.96% of control group respectively. Meanwhile, B. tabaci damage reduced the total dry matter weight of tomato. For example, after twenty-eight days the total dry matter weight of tomato treatment 1 and 2 ware 68.36% and 41.47% of control group respectively.The strong seedling index and relative growth rate of the treatment were significantly lower than control.2、The influence of nutrient constituents of the tomato fruit fed by B. tabaci was studied.In order to investigate the effects of B. tabaci on fruit quality of tomato, the different developmental stages of tomatoes were inoculated by a certain number of B. tabaci. The results demonstrated with the increase of B. tabaci damaged, vitamin C (Vc) in the fruit of tomatoes was decreased obviously, and the rates of decline of Vc were from 15.36%～52.74% under different inoculation densities of B. tabaci. The lower population densities of the pests would increase the protein contents while higher population densities made it decrease, and the lowest content was only 33.67% of the control. When lower population densities of the pest, with the growth of population densities, the amount of amino acids rose significantly. But over grade 3, the amount of amino acids decreased, and there was no significant difference between the control group and the damage grade 4 and 5. In contrast to, the contents of cystine, phenylalanine, histidine and praline showed an increased tendency, when the number of B. tabaci population was high. Under different densities of B. tabaci, the soluble sugar contents of tomato fruits decreased from 9.83% to 62.31%. The organic acid contents and the ratio of sugar to acid in tomatoes fruits also were declined significantly, accompanying by increase of the damage. And the organic acid contents and the ratio of sugar to acid at the mature stage were higher than the green ripe stage.3. The variation of biochemical composition of tomato plant by the damage of B. tabaci was studied.To detect the effect of different pest density on the physiology and biochemistry of tomatoes damaged by B. tabaci, ninth leaf stage tomatoes were inoculated by distinct numbers of B. tabaci. The physiological indexes of root activity, photosynthesis rate, pollen vitality of plant and biochemical index of chlorophyll, soluble sugar, soluble protein in plant were measured. The results showed no matter the high density (450 individuals per plant) or low density (50 individuals per plant), the root activity and photosynthetic rate, pollen vitality physiological indexes were significantly decreased. After inoculated by B. tabaci, the chlorophyll content and soluble sugar content of the infested plant are significantly lower than the control, which may be the synthesis of chlorophyll and photosynthesis blocked inside its body. Under the adversity of the damaged by B. tabaci b, the enrichment of a lot of proline content in the body; the soluble protein content in low density (50 individuals per plant) have a little rise, while the soluble protein content in other plants were significantly lower than the control. However, through the determination of the different oxidase of tomato, different enzymes of tomato plants to B. tabaci damage responses were vary. SOD activity reached the maximum when whitefly infestation at 6 days, and its growth rate significantly higher than the control, the activity decreased after infestation at 9 days. The POD activities increased with the days after treat and the insect density. The high density treatment on the 3rd,6th,9th day after damage, the values of the POD activities were 130.66%,163.94%,184.75% respectively compared with the control. After treat for 3-6 days, the tomato in vivo CAT activity reached the maximum, while the activity of CAT of low density treatment was significantly lower than high density treatment. In the same period of infestation, with the increase of amount of pests, the activity of PAL enzyme activity increased, damage after 9 days, high density treatment and low density treatment were 134.80%, 180.25% respectively. The PPO activities of tomato seeding leaf increased with the days after treat, and the PPO activity of low density treatment is always higher than that high density treatment.4. The adaptability mechanism of B. tabaci to different tomato varieties was determined.Through the study of the natural selectivity of B. tabaci to 20 kinds of tomato varieties under indoor and outdoor condition, the results showed that the selectivity of B. tabaci to various tomato varieties were significant different. The number of adults of B. tabaci on the LvJian 2 was significantly much more than other tomato varieties. In the outdoor, the number of adults of B. tabaci on the Jingpinshujiao was significantly less than other tomato varieties. The selection of B. tabaci to Suhong 2003, Jinglinghongyu, Shitoudafen were different. Based on five representative varieties, according to the population life table, spawning, generation net reproductive rate and intrinsic rate of B. tabaci were significantly higher on LvJian 2 than other varieties, and Jingpinshujiao and Jinglinghongyu were the lowest among all varieties. Determination of the adults of B. tabaci olfactory response to five representative tomato varieties suggested that the adults of B. tabaci showed the positive tend to the lvjian 2 and Jinglinghongyu, negative tend to the Suhong 2003, and with no obvious tend to the Jingpinshujiao and Shitoudafen. Through Gas Chromatography -Mass Spectrometry test,15 kinds of volatile matter from different tomato varieties was detected. Among them, six kinds of volatile matter including cineole, β-phellandrene, Myrcene, β-pinen, α-pinen, β-caryophyllene. have obvious stimulation to the sense of smell of B. tabaci. The volatile matter content of lvjian 2 was significantly higher than others, so B. tabaci has the positive tends to it. The volatile matter content of Jinglinghongyu was low, but the content of cineole, β-phellandrene, Myrcene, β-pinen were high, which have attraction effect to B. tabaci, so B. tabaci also has the positive trends to it. The total volatile matter content of Jingpinshujiao was low, so B. tabaci has no obvious positive trends to it. Thus above results provided internal mechanism for which lvjian 2 is sensitive varieties, Jinglinghongyu and Jingpinshujiao are resistant varieties, Suhong 2003 and Shitoudafenare were mid- resistant varieties.5. The economic threshold and the techniques of chemical control of B. tabaci on tomato were studied.According to the different densities of B. tabaci on the harm to tomato, the economic threshold of B. tabaci harm to tomato were studied. The results showed that there was significant correlation between densities of B. tabaci and the individual products number, per fruit weight, individual plant productivity of tomato. With the increase of B. tabaci population density, the individual products number decline exponential, the per fruit weight decline on a linear. By calculating, the control index was 5.21 B. tabaci on per square centimetr. To understand the effective modes and mechanisms of nitenpyram, bioassay and continuous immersion methods were used to study the death rate and detoxification enzyme activities of B. tabaci under different treatments in the room. The results showed that nitenpyram possessed intake transportation activity and contact toxicity for B. tabaci, and the death rates of nymphs and adults treated with intake transportation and contact toxicity were 90.60%,84.89% 79.90% and 73.27%, respectively. Spraying and irrigating root applications showed better. From the rapidly available, spray is better than root irrigation, while from effect holding, root irrigation is higher than spray, and effect of spraying and irrigating root applications both higher significantly than dipping one leaf and smearing. The activity of carboxylesterase in B. tabaci reated with LC50 concentration of nitenpyram was reversible inhibition. After 24 h, the activity of carboxylesterase of B. tabaci treated with nitenpyram wasn’t change significantly comparing to untreated B. tabaci (control), but the activity of carboxylesterase was elevated at 48h. The activity of acetylcholinesterase in B. tabaci treated with nitenpyram was decreased till 36 h, and its specific activity was decreased about 20.00% (P<0.05) at last. The activity of glutathione-S-transferase was decreased with the increase of treated time, and its specific activity decreased 7.00% (P<0.05) at 48 h. |
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