研究茉莉酸甲酯(MeJA)和日本龟蜡蚧诱导柿树挥发物对天敌昆虫红点唇瓢虫的吸引作用。结果显示:7月份当日本龟蜡蚧处于若虫阶段时,它的危害并不能诱导柿树对瓢虫的吸引;相反,用茉莉酸甲酯处理过的柿树表现出对瓢虫明显的吸引,呈现升高—降低—再升高的波动变化。在MeJA处理后的8h(当天15:00)和24h(第2天早7:00)达到高峰期,其对瓢虫的吸引率分别为78.21%和73.42%。通过GC/MS分析,从MeJA处理的柿树和对照中共检出4类17种化学成分。2[10]-蒎烯和柠檬油精是在处理柿树中新增加的成分。另外3种萜类化合物的相对含量增加,其中α-蒎烯最为明显。这些挥发物组成的变化揭示了柿树吸引瓢虫的原因。根据对化学成分的分析,选择单组分柠檬油精和α-蒎烯来验证它们对红点唇瓢虫的吸引力。结果证明,两者对该瓢虫都有明显吸引力,在浓度为1×10^-4和1×10^-5g·mL^-1时的吸引率分别为78.95%和75.61%。因此认为,MeJA可以作为一种信号转导分子用于诱导寄主植物释放挥发物,提高对蚧虫的生物防治效果。此外,发现萜类化合物在一天中的波动变化。直到MeJA处理后的8h,6种萜类物质的含量都增加,但到了12h,只检出α-蒎烯其含量为0.87%。然而到第2天早上7:00,所有6种萜类化合物又都重新检测到,其中α-蒎烯甚至达到了73.01%。
We studied the response of the ladybeetle, Chilocorus kuwanae, to volatiles released by persimmon trees (Diospyros kaki) induced either by an attack of Japanese wax scales, Ceroplastesjaponicus, or by an exogenous methyl jasmonate (MeJA) application. Results showed that, when C. japonicus was at the young nymph stage in July, its attack was not able to induce persimmon trees to attract ladybeetles. In the contrast, persimmon trees after sprayed with MeJA displayed a significant attraction to the ladybeetles, which showed a fluctuation rhythm of increase-decrease-increase again. The peaks of attractive responses were 78.21% at 8 h (15:00) and 73.42% at 24 h (7:00 next morning) after the MeJA treatment. A total of 17 chemical components were detected by GC/MS from the volatiles of MeJA-treated or control persimmon trees. Among those chemicals, 3 terpenoid components were higher in MeJA-treated trees than that in control trees, and 2[ 10]-pinene and D-limonene were detected only from the volatiles of MeJA-treated persimmon trees. These differences in the volatile compositions suggested the possible reason for the attraction of the treated persimmon trees to the ladybeetles, which was futher confirmed by the ladybeetle attraction experiment with those chemicals. Both D-limonene and α-pinene displayed a significant attractiveness (78.95% and 75.61%, respectively) at concentration of 1 × 10^-4 and 1 × 10^-5 g·mL^-1. Therefore, it is suggested that blGA as a signal transducer may be a potential agent in regulating volatile emissions of the host plant and improving biological control of scale insects. The fluctuation in amounts of terpenoid compounds was also found in the MeJA-treated trees. Up to 8 h after treatment, the relative content of 6 terpenoids all increased, but to the 12 h only 0.87 % α-pinene was detected. However to next 7:00 am, the 6 terpenoids were detected again and among them α-pinene even reached 73.01 %.