人类基本呈味物质对菜粉蝶幼虫的拒食作用

呈味物质是人类经过漫长筛选形成的味感强烈的物质,可能在调控害虫取食行为中发挥重要作用,但传统的二分式定性法难以阐明其对昆虫味觉反应的复杂相互作用。为此,以菜粉蝶为研究对象,采用叶碟法结合正交设计测试了6种人类呈味物质(柠檬酸、蔗糖、奎宁、氯化钠、山椒醇和辣椒素)对菜粉蝶幼虫取食反应的影响。单一呈味物质与对照叶碟的配对测试表明,拒食反应指数较高的呈味物质为柠檬酸(93.89%)、奎宁(90.33%)、山椒醇(83.33%),但正交测试却发现辣椒素、蔗糖、山椒醇影响较大,且奎宁和氯化钠可能相互拮抗。进一步采用对菜粉蝶幼虫取食量影响较大的4种呈味物质进行选择性取食和非选择性取食测定,发现辣椒素效应最大。2种条件下均表现出较强拒食活性的样品组合为蔗糖9μL+山椒醇9μL+辣椒素3μL+柠檬酸12μL。结果表明,特定呈味物质在单剂刺激和混合刺激下的表现存在较大差异,利用多因素试验设计方法优化多元组分的拒食剂,可能有助于解决害虫味觉反应习惯化的问题。

Feeding Deterrence of Six Basic Tastants against Pieris rapae Larvae

Tastants are serials of heavy-taste substances screened out by human beings for a long time,which may play an important role in the regulation of feeding behaviours of herbivoral insects.However,the either-or characterization of these substances with respect to their effects on feeding response of herbivores is not efficient to explain the comprehensive interactions among various tastants.This study tested the feeding deterrence of six tastants(citric acid,sucrose,quinine,NaCl,sanshool,and capsaicin),alone or orthogonally combined,against Pieris rapae larvae.The paired bioassay with each tastant and control leaf disc indicated that citric acid,quinine,and sanshool evoked strong feeding deterrence,with feeding deterrence values of 93.89%,90.33%,and 83.33%,respectively.When these tastants were orthogonally combined,capsaicin,sucrose,and sanshool exhibited stronger effects on the feedingamount,while quinine and NaCl acted antagonistically.Four tastants showing relatively stronger effects were orthogonally combined further and tested under selective and non-selective feeding conditions.The result showed that capsaicin exhibited the strongest feeding deterrence,and only one sample(9 μL sucrose + 9 μL sanshool + 3 μL capsaicin + 12 μL citric acid) exhibited strong feeding deterrence under both conditions.A given tastant could show remarkable discrepancy when used alone or combined,suggesting that some multiple-factor experimental designs should be introduced in insect feeding bioassay to overcome the gustatory habituation of pests.