施硅对水稻抗虫性的影响及其机制：不同取食习性害虫间的比较

Silicon plays an important role in improving plants' tolerance to abiotic and biotic stresses, and rice is known as 'silicate plant'. However, the roles of silicon in regulating rice plant resistance to insect pests are not much addressed, even less of the mechanisms underlying the resistance regulation. Focusing on rice and insect pests of different feeding habits, i.e. the striped stem borer, the rice leaf roller and the brown planthopper, the current project intends to measure the effects of silicon addition on oviposition and feeding preference and on feeding and development of the insect pests to elucidate the silicon-mediated mechanisms of constitutive defence against rice insect pests of different feeding habits. Also, the project will measure the effects of silicon addition and pest damage on resistance-related physiological process to unravel silicon-mediated mechanisms of inductive defence against rice insect pests of different feeding habits. And last, the project will determine the effects of silicon amendment on tolerance of rice to insect pest damage and on pest population dynamics in the field. Differing from the previous researches focusing on a single insect pest and/or a single resistance mechanism, this project will unravel the whole silicon-mediated mechanisms of rice resistance to insect pests and define the roles of silicon addition in regulating populations of insect pests of different feeding habits, which will help to extend the use of silicon in rice production.

硅在提高植物对非生物和生物胁迫的适应性上具有重要作用，水稻素有"硅酸植物"之称。但是，硅调节水稻对不同取食习性害虫的抗虫性尚缺乏全面的研究，硅介导的水稻对不同取食习性害虫抗虫性的机制更没有研究报道。本项目针对水稻与不同取食习性害虫（二化螟、稻纵卷叶螟和褐飞虱），测定施硅对害虫产卵和取食选择性的影响及机制、对害虫取食和发育的影响及机制，阐明施硅调节水稻对不同取食习性害虫的组成性防御的机制；测定施硅和害虫为害对水稻诱导抗虫性及其相关生理机制的影响，揭示施硅调节水稻对不同取食习性害虫的诱导性防御的机制；测定施硅对水稻耐受害虫为害的影响、对害虫种群动态的调控作用，明确施硅对水稻上不同取食习性害虫种群的调节作用。本申请项目突破针对单一害虫和单一抗虫机制的研究模式，将阐明硅调节水稻对不同取食习性害虫抗虫性的完整机制，明确施硅对水稻上不同取食习性害虫种群的调控作用。

本项目设置施硅水稻和不施硅水稻，开展一系列研究，取得了如下主要结果。1）施硅降低二化螟和稻纵卷叶螟的适合度。施硅抑制二化螟幼虫钻蛀，在感虫品种上效果更高。施硅降低稻纵成虫的产卵选择性和幼虫的取食选择性。施硅显著降低稻纵卷叶螟种群增长，延长种群加倍时间；降低卷叶株率和卷叶率。2）从营养生态、水稻防御反应和稻纵卷叶螟生理适应性等方面阐明了施硅增强水稻对稻纵卷叶螟抗性的机制，施硅水稻上稻纵卷叶螟的取食量和相对取食率高，而相对生长率、近似消化率、食物利用率和食物转化率反而低。这是由于施硅水稻叶片的可溶性糖含量和碳氮比高，而氮含量低。施硅增强水稻对稻纵卷叶螟取食胁迫的防御反应，显著降低受害叶的可溶性蛋白质和丙二醛含量，提高CAT、POD、SOD、PPO和PAL的活性。施硅引起稻纵卷叶螟幼虫保护酶（CAT、POD、SOD）和解毒酶（GST、AChE）活性的变化，不利于其存活。3）施硅降低褐飞虱的适合度和种群增长。施硅水稻上褐飞虱的若虫存活率、成虫寿命、产卵量和性比降低，发育历期延长，褐飞虱种群的内禀增长率、周限增长率和净增殖率降低。4）从害虫行为、植物抗虫生理和组织形态学机制等方面阐明了施硅增强水稻对褐飞虱抗虫性的机制，发现褐飞虱成虫对施硅水稻的取食选择性和取食量下降，因为施硅阻碍褐飞虱的刺吸行为，施硅在一定程度上放大褐飞虱取食胁迫诱导的水稻防御反应，施硅显著增大稻茎的硅化程度和受害叶鞘的韧皮部筛管胼胝质（callose）沉积量，后者是由于硅上调了受害稻株的胼胝质合成酶基因OsGSL1的相对表达而下调了降解酶基因GNS5的相对表达。5）采用小区试验，明确了施硅对水稻主要害虫与病害种群与为害和产量的影响，施硅小区病虫害发生和为害有不同程度的下降，水稻结实率和千粒重显著增大、产量有小幅增长。这些结果阐明了施硅可增强水稻对多种害虫的抗虫性及其机制，明确了施硅增强水稻对不同取食习性害虫抗性的共同机制及其差异，为采用硅来调控水稻害虫奠定了理论基础。