茶树花挥发物对叶蝉三棒缨小蜂的引诱增强效应

茶树(Camellia sinensis)是我国重要的经济作物。小贯小绿叶蝉(Empoasca onukii)是为害茶树的主要害虫之一。叶蝉三棒缨小蜂(Stethynium empoascae)是小贯小绿叶蝉的主要卵寄生蜂, 但茶树花对叶蝉三棒缨小蜂的引诱机制尚不明确。基于析因设计的方差分析结果显示, 茶树花可引诱天敌叶蝉三棒缨小蜂, 显著缩短其寄生行为的搜寻时间。茶树花可显著增强叶蝉为害茶梢对缨小蜂的吸引作用, 而对健康茶梢的增强效应不显著。基于气相色谱-质谱(GC-MS)的结果显示, 健康茶梢中的挥发物种类和相对含量较少, 而叶蝉为害茶梢和茶树花中挥发物种类和相对含量显著增多。偏最小二乘法判别分析(PLS-DA)结果显示, 茶树花挥发物具有明显的聚类特征。变量重要性投影结果表明, 17种茶树花挥发物在判别分析中可能起重要作用。行为测定结果显示, α-水芹烯、顺式氧化芳樟醇、反式氧化芳樟醇、苯甲醛和苯乙酮对叶蝉三棒缨小蜂具有显著的引诱效果。研究初步阐明了茶树花通过释放挥发物引诱叶蝉三棒缨小蜂的机制, 为制定叶蝉的生物防治策略提供了理论依据。

Enhanced Attraction of Mymarids (Stethynium empoascae) by Volatiles from Tea Flowers

The tea plant (Camellia sinensis) is an important economic crop in China. Tea green leafhopper (Empoasca onukii) is the most damaging pest of tea plants and mymarid (Stethynium empoascae) has been classified as its egg parasitoid. However, the mechanism underlying the olfactory attraction of mymarids by tea flowers is still elusive. By factorial design, we showed that tea flowers could attract mymarids which are natural enemies of leafhopper and accelerated the parasitic behavior of mymarid. Tea flower specifically decreased the search time of parasitic behavior of mymarid with tea shoots infested by leafhoppers. However, the boosting effect of tea flower was lost in healthy tea shoots. Compared with health tea shoots, the types and relative contents of volatiles were dramatically increased in infested tea shoots using gas chromatography-mass spectrometry (GC-MS). We classified the volatile expression patterns of healthy tea shoots, infested tea shoots and tea flowers using partial least squares discrimination analysis (PLS-DA). Based on variable importance for the projection (VIP), and identified 17 tea flower volatiles which could potentially discriminate the patterns of volatiles in the three tissues. Olfactometer bioassay showed that α-phellandrene, cis-linaloloxide, trans-linaloloxide, benzaldehyde and acetophenone significantly attract mymarids. Our work has preliminarily demonstrated the defense mechanism mediated by tea flowers and provides novel clues for biological control of tea green leafhopper management.