Hawthorne David J
Department of Entomology, University of Maryland, College Park, MD 20742, USA.
J Econ Entomol. 2003 Aug;96(4):1021-30. doi: 10.1093/jee/96.4.1021.
Quantitative trait locus (QTL) mapping is a valuable new tool for locating genomic regions that underlie variation in important traits such as insecticide resistance. Because QTL mapping complements a candidate gene strategy for understanding the genetic architecture of important traits, it may also facilitate the identification of genes causing important variation. After mapping the QTL locations, markers closely linked to QTL can be used for genetic analysis of population structure and to measure the spread and increase of resistance-causing QTL alleles. In this study, QTL influencing resistance to the pyrethroid insecticide esfenvalerate were mapped in the Colorado potato beetle Leptinotarsa decemlineata (Say) (CPB). Three QTL contributing to esfenvalerate resistance were identified from a mapping population of 79 individuals analyzed at 90 marker loci. One QTL had a large effect and two QTL had smaller effects. The major QTL occurs on the X chromosome, overlapping the position of a candidate gene (Leptinotarsa decemlineata Voltage sensitive sodium channel [LdVssc1]) previously implicated in pyrethroid resistance. Resistance-increasing alleles at the two minor-effect QTL originated with the susceptible parent, suggesting that alleles of small effect may be segregating in susceptible populations. Comparison of the New York population from which the susceptible parent originated with a more-susceptible population from North Carolina suggests that the minor-effect loci identified here may explain some of the variation in tolerance observed among susceptible populations. DNA sequencing of a portion of LdVssc1 shows that the resistance-conferring allele from the resistant parent does not contain the kdr mutation previously found in CPB and typically observed in other insects that are resistant to pyrethroid insecticides because of changes in this gene.
数量性状基因座（QTL）定位是一种有价值的新工具，可用于定位重要性状（如抗杀虫剂性）变异背后的基因组区域。由于QTL定位补充了用于理解重要性状遗传结构的候选基因策略，它也可能有助于鉴定导致重要变异的基因。在定位QTL位置后，与QTL紧密连锁的标记可用于群体结构的遗传分析，并测量导致抗性的QTL等位基因的传播和增加。在本研究中，对影响拟除虫菊酯类杀虫剂乙氰菊酯抗性的QTL在科罗拉多马铃薯甲虫Leptinotarsa decemlineata（Say）（CPB）中进行了定位。从一个由90个标记位点分析的79个个体的定位群体中鉴定出了三个导致乙氰菊酯抗性的QTL。一个QTL具有较大效应，两个QTL具有较小效应。主要QTL位于X染色体上，与先前涉及拟除虫菊酯抗性的候选基因（Leptinotarsa decemlineata电压敏感钠通道 [LdVssc1]）的位置重叠。两个小效应QTL的抗性增加等位基因起源于易感亲本，这表明小效应等位基因可能在易感群体中分离。对易感亲本来源的纽约群体与北卡罗来纳州一个更易感群体的比较表明，这里鉴定出的小效应基因座可能解释了易感群体中观察到的部分耐受性变异。LdVssc1一部分的DNA测序表明，抗性亲本的抗性赋予等位基因不包含先前在CPB中发现的kdr突变，并且通常在其他因该基因变化而对拟除虫菊酯类杀虫剂产生抗性的昆虫中观察到。
