Faccoli Massimo, Anfora Gianfranco, Tasin Marco
Department of Environmental Agronomy and Crop Sciences-Entomology, Agripolis-Viale dell'Università 16/a, Legnaro, Padua, Italy.
J Chem Ecol. 2008 Sep;34(9):1162-9. doi: 10.1007/s10886-008-9503-6. Epub 2008 Aug 14.
The pine shoot beetle Tomicus destruens has two dispersal phases per generation. In the first, mature adults move toward trunks of dying pines to lay eggs; in the second, callow adults move toward the shoots of healthy pines for maturation feeding. However, there is no information on the chemical stimuli that govern host selection by T. destruens adults. The aims of this study were: (1) to identify the volatiles released by shoots and bark of stone pine that are behaviorally and electrophysiologically active on T. destruens; (2) to verify which blends and concentrations of such volatiles are differently active on males and females, as well as on callow and mature adults, during the two host search phases (breeding and feeding). A four-arm olfactometer was used to test the behavior of walking T. destruens adults toward various sources of volatiles including fresh shoots and bark, their collected volatiles, and two synthetic blends. For each odor, the behavior of both callow and mature males and females was recorded individually. Shoot and bark extracts were analyzed by coupled gas chromatography and mass spectrometry (GC-MS), and tested by gas chromatography coupled with electroantennography (GC-EAD) on T. destruens males and females. Two blends of two (alpha-pinene and beta-myrcene; blend A) and three (alpha-pinene, beta- myrcene, and alpha-terpinolene; blend B) synthetic compounds, chosen among those that induce EAD responses and known to be attractive for other bark beetle species, were tested in the olfactometer at five concentrations. Insect behavior was affected by the degree of sexual maturation but not by sex. Callow insects were attracted by shoots and their extracts, while mature individuals by bark and its extracts. Six extracted compounds were active on T. destruens antennae: limonene, (Z)-3-hexen-1-ol and beta-caryophyllene, alpha-pinene, beta-myrcene, and alpha-terpinolene. alpha-Terpinolene, released only by bark, was active only on mature insects, whereas (Z)-3-hexen-1-ol, released only by shoots, was active only on callows. Males and females showed similar EAD responses. Of the six extracted volatiles, two were attractive for callow adults (blend A) and three for matures (blend B). In both cases, responses were positively correlated with blend concentration, although a repellent effect was noted at the highest concentrations.
松树梢小蠹（Tomicus destruens）每代有两个扩散阶段。在第一个阶段，成熟成虫向濒死松树的树干移动以产卵；在第二个阶段，新羽化的成虫向健康松树的嫩梢移动以进行成熟取食。然而，关于调控松树梢小蠹成虫寄主选择的化学刺激物尚无相关信息。本研究的目的是：（1）鉴定瑞士石松嫩梢和树皮释放的、对松树梢小蠹具有行为活性和电生理活性的挥发物；（2）验证在两个寄主搜寻阶段（繁殖和取食）中，这些挥发物的哪些混合物及浓度对雄性和雌性、新羽化的成虫和成熟成虫具有不同的活性。使用四臂嗅觉仪测试行走的松树梢小蠹成虫对各种挥发物来源的行为反应，这些挥发物来源包括新鲜嫩梢和树皮、它们收集到的挥发物以及两种合成混合物。对于每种气味，分别记录新羽化的成虫和成熟的雄性及雌性的行为。对嫩梢和树皮提取物进行气相色谱 - 质谱联用（GC - MS）分析，并通过气相色谱 - 触角电位联用（GC - EAD）对松树梢小蠹的雄性和雌性进行测试。从那些能诱导EAD反应且已知对其他小蠹虫有吸引力的化合物中选择了两种（α - 蒎烯和β - 月桂烯；混合物A）和三种（α - 蒎烯、β - 月桂烯和α - 萜品烯；混合物B）合成化合物，在嗅觉仪中以五种浓度进行测试。昆虫的行为受性成熟程度影响，但不受性别影响。新羽化的昆虫被嫩梢及其提取物吸引，而成熟个体被树皮及其提取物吸引。六种提取的化合物对松树梢小蠹触角有活性：柠檬烯、（Z）-3 - 己烯 - 1 - 醇、β - 石竹烯、α - 蒎烯、β - 月桂烯和α - 萜品烯。仅由树皮释放的α - 萜品烯仅对成熟昆虫有活性，而仅由嫩梢释放的（Z）-3 - 己烯 - 1 - 醇仅对新羽化的昆虫有活性。雄性和雌性表现出相似的EAD反应。在六种提取的挥发物中，两种对新羽化的成虫有吸引力（混合物A），三种对成熟成虫有吸引力（混合物B）。在这两种情况下，反应都与混合物浓度呈正相关，尽管在最高浓度时观察到有驱避作用。
