| The Chinese fruit fly, Bactrocera minax, is an important pest of citrus fruit that belongs to the genus Bactrocera within the family Tephritidae of the order Diptera. It has been reported in multiple districts of China including Chongqing to seriously affect the development of citrus production, and the damage extent displays an aggrevating trend. The thesis studied effects of different temperature treatments on the development of B. minax larvae and pupae, determined the hormone contents in last instar larvae and pupae at that time, and inquired into effects of the juvenile hormone analogues and moulting hormone on the pupation and eclosion so as to find out the hormonal regulation mechanisms of terminating diapause and advancing eclosion of B. minax.This project was supported by the National Basic Research Program of China (2009CB125903) and the Special Fund for Agro-scientific Research in the Public Interest (200903047-4). The main results of the research were as follows:1Effect of the temperature on B. minax larvaeTo observe the effect of the temperature on the pupation and eclosion of B. minax larvae, we set five different constant temperature treatments, different temperature cycles including four alternating temperature combinations and four alternating time combinations, different low temperature treatments and different durations with the3rd larvae as the research object in this study. The results showed that all the tested larvae under5℃,10℃,15℃,20℃and25℃were pupated. The larvae pupation rates reached up to100%under15℃,20℃and25℃, and the rates declined significantly under5℃and10℃. The larvae could pupate under5℃, but the pupae could not complete the eclosion behavior. The eclosion rates were63.3%and53.33%under15℃and20℃, repectively, higher than the other two temperature treatments. The eclosion rates were33.33%and31.67%under10℃and25℃, repectively, lower than the above two temperature treatments. The larva duration shortened and the pupa duration extended with the temperature rising. The study indicated that the pupation rates and eclosion rates of B. minax larvae declined significantly under10℃or lower temperature and that15℃and20℃were the optimum temperature for the larvae pupating and the pupa emergencing.The pupa durations under different temperature cycles were significantly different. The pupation duration was shortest when the alternating temperature combination was20℃:5℃with5.25d, which was significantly different from8.75d under25℃:5℃ and7.25d under25℃:10℃. However, the pupation rates and eclosion rates were not. The pupation rates were all over91.67%, and the eclosion peak date was focused between April16th and April27th under different temperature cycles.The pupation rates of B. minax larvae through different days of low temperature were different under5℃and15℃. The pupae could not complete the eclosion behavior under20d of5℃. Under the tested low temperature, the pupation rates and eclosion rates of B. minax3rd instar displayed a decreasing trend with the treatment time extending.2Effect of the temperature on B. minax pupaeThe chapter firstly divided the pupae of of B. minax into the pupae before the new year and the pupae after the new year. The results showed that the pupae before the new year couldn’t complete the eclecion behavior under25℃, while the pupae after the new year could. The eclosion rates between the pupae before and after the new year were significantly different under all different constant temperature, and the rates of the pupae after the new year were higher. Both of the two types of pupae reached the highest eclosion rates under15℃and the rates were53.33%and86.77%, respectively. The eclosion durations and peak days of the pupae after the new year were shorter under5constant temperature. The eclosion progress of the pupae after the new year was earliest under25℃, later under20℃, and latest under5℃.There existed a certain impact on the eclosion progress of B. minax pupae under different temperature cycles. The results showed that the eclosion time of the pupae after the new year was relatively concentrated and advanced under different temperature cycles, and the beginning, apex and end of the eclosion period of B. minax pupae after the new year were advanced15days. Under the temperature cycle combinations, the eclosion rates of the pupae before the new year reached highest as58.33%when it was20℃:10℃and14h:10h, and the eclosion rates of the pupae after the new year reached highest as76.67%when it was25℃:10℃and12h:12h. The eclosion rates between the pupae before and after the new year were significantly different under different low temperature treatments, and the eclosion rates of the pupae after the new year were higher than that of the pupae before.3Determination of juvenile hormone and moulting hormone in B. minaxThe contents of MH and JH-Ⅲ were both influenced under different constant temperature and alternating temperature in different stages of B. minax. The MH contents in the last instar larvae and the pupae after the new year were higher than that in pupae after and during the new year, which was in other words that the MH contents in B. minax before pupation and eclosion were higher. The JH-III contents decreased with the extension of pupa duration. During the whole pupa stage, the levels of MH and JH-Ⅲ was negatively correlated in the range of5℃to10℃and was positively correlated in the range of10℃to25℃, which indicated that the lower the temperature in the range of10℃to25℃, the shorter the pupa duration, which was meaned by that the eclosion of B. minax was advanced. The results also proved that MH was dominant in the eclosion of B. minax, laying foundations for the exogenous hormone regulation of B. minax advancing the eclosion.4The effect of exogenous juvenile hormone and moulting hormone on B. minaxIn this study, the effects of five different dosages of exgenous JH and MH on the pupation rates and eclosion rates of B. minax were discussed through the micro-drop and micro-injection method. The results showed that the pupation rates did not change after the JHA and MH treating B. minax larvae and that the eclosion rates both increased with JHA more effective. JHA treatment could not make B. minax larvae and pupae complete the eclosion behavior in advance as well as the eclosion progress. MH treatment had no effects on eclosion of the larvae and pupae before the new year, but could make the pupae after the new year complete the eclosion behavior in advance and promote their eclosion progress. After the MH treatment, the dosage of the earliest eclosion peak was0.5ug/head, later1.0ug/head, and the latest0.05ug/head, which were advanced15d-45d compared with the other treatments. |
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