施硅玉米对草地贪夜蛾的影响

【目的】研究取食外源施硅的玉米对草地贪夜蛾（Spodoptera frugiperda）生长发育的影响，并探究施硅玉米被草地贪夜蛾取食后其防御酶活性的变化，为外源施硅提高作物抗虫能力提供实践范本和理论参考。【方法】以采集自福建省漳州市的草地贪夜蛾为研究材料，对玉米施以不同浓度（1）对照（CK）（0 g Si/kg土），（2）5倍施硅处理（3.85 g Si/kg土），（3）10倍施硅处理（7.70 g Si/kg土）]的硅肥，观察施硅对玉米生长发育的影响；将初孵草地贪夜蛾幼虫分别接在不同施硅处理的玉米植株上，至3龄后以7 d为一个周期调查记录草地贪夜蛾体重、体长、发育历期、化蛹率、蛹重和羽化率；利用试剂盒测定被草地贪夜蛾取食前后的玉米植株体内超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和多酚氧化酶（PPO）活性变化。【结果】增施硅肥短期内（21 d）有助于玉米株高和茎粗的生长，其中对玉米茎粗生长有显著的促进作用（P<0.05，下同）。取食外源施硅玉米影响了草地贪夜蛾的生长发育，在处理第21 d时取食10倍硅浓度处理玉米的草地贪夜蛾幼虫体重最轻，只有0.2023 g，显著低于CK，且较CK的发育历期显著延长26.02%，羽化率显著下降27.78%。玉米经不同硅浓度处理后，未被取食的玉米植株体内SOD、CAT和PPO活性均以10倍施硅处理最高，其中SOD和PPO活性均显著高于CK和5倍施硅处理，CAT活性在3种处理间无显著差异（P>0.05，下同）；被草地贪夜蛾取食后24 h时，3个硅浓度处理间玉米植株体内的SOD活性无显著差异，而CAT和PPO活性均以10倍施硅处理玉米最高，且均显著高于CK和5倍施硅处理。相关性分析结果表明，玉米叶片的防御酶（SOD、CAT和PPO）活性与草地贪夜蛾体重呈负相关关系，即防御酶活越高，草地贪夜蛾体重越轻。【结论】外源施硅可通过提高玉米植株体内SOD、CAT和PPO等防御酶的活性以参与玉米对草地贪夜蛾的防御响应。

Effects of silicon application in corn on Spodoptera frugiperda(J. E. Smith)

【Objective】To study the effects of feeding exogenous silicon-applied corn on the growth and development of Spodoptera frugiperda(J. E. Smith), and to explore the change of defense enzyme activity of S. frugiperda after feeding siliceous corn to provide a theoretical basis for the study of silicon application to improve plant resistance to pests.【Method】Using S. frugiperda collected in Zhangzhou, Fujian as the research material, different concentrations of silicon fertilizer were applied to corn(1) control(CK) group(0 g Si/kg soil, (2) 5-time silicon treatment group(3.85 g Si/kg soil) and(3) 10-time silicon treatment group(7.70 g Si/kg soil)]. First, observed the effects of silicon application on the growth and development of corn, and then larvae of the newly hatched S. frugiperda were put to the maize plants treated with different silicon treatments, and recorded the insect weight, body length, development period, pupation rate, pupa weight and emergence rate every 7 d after the larvae grew to the third instar, and used the kit to determine the superoxide dismutase(SOD), catalase(CAT) and polyphenol oxidase(PPO) in corn before and after being eaten by S. frugiperda.【Result】Short-term application(21 d) of silicon increased the plant height and stem circumference of corn, and significantly promoted the growth of stem circumference of corn(P<0.05, the same below). Feeding exogenous silicon application on corn affected the growth and development of S. frugiperda. The larval weight of 10-time silicon concentration on corn on the 21st day of the experiment was the lightest, only 0.2023 g, which was significantly lower than that of the CK, and the development period prolonged 26.02% compared with the CK, the emergence rate significantly decreased by 27.78%. The SOD, CAT and PPO activities in unfed corn plants were the highest treated by 10 times silicon application after corns were treated with different silicon concentrations. SOD and PPO activities were significantly higher than CK and 5-time silicon application, SOD, and CAT activity had no significant difference among the three treatments(P>0.05, the same below). 24 h after the corn being fed, SOD activityamong the three treatments had no significant difference, but CAT and PPO activities in 10-time silicon application were the highest, and significantly higher than CK and 5-time silicon application. Correlation analysis showed that the three defensive enzyme(SOD, CAT and PPO) activities of corn leaves were negatively correlated with the body weight of S. frugiperda, that was, the higher the defensive enzyme activity, the lighter the weight of S. frugiperda.【Conclusion】Exogenous application of silicon fertilizer can increase the activity of defensive enzymes(SOD, CAT and PPO) in corn, thereby enhancing the defense ability of corn against S. frugiperda.