维系爱玉子与其传粉小蜂共生体系的化学生态学机制

Ficus awkeotsang Makino is a special fruit tree species introduced from Taiwan. This fig tress has a stable mutualistic relationship with its pollinator, Wiebesia pumilae (Hill) Wieb (Hymenoptera: Chalcidoidea Agaonidae). Lacking of pollinating fig wasps would definitely break down the pollination chain and lead to damaging of the mutualism system. The preciseness of wasp's locating its host (F. awkeotsang) is a prerequisite criteria for restoring and maintaining of the symbiotic system. Volatile compounds from the syconia of F. awkeotsang plays an importatn role in chemical recognition and host-location of pollinating wasps. However, little is known about the mechanism of interactions between these pair species. In this study, we will 1) investigate the relationship between developmental phases of syconia and volatiles emitted from them, as well as the geographic variation of syconia developmental process in male and female figs of F. awkeotsang; 2) investigate the spatial and temporal variation of the volatile compounds from the syconia through dynamic headspace sampling technique coupled with gas chromatography and mass spectrometry analysis method; 3) combining insect electroantennography technology with experiments on preference choice of fig wasps on various olfactory cues, we want to elucidate the association between various volatile compounds and the host selection of pollinating fig wasps. Thus we may be able to clarify the chemical mechanism of mutualistic interactions between fig and their pollinating wasps, and uncover the special pheromone formula which can attract pollinating wasps and then enhance the efficiency of chemical recognition and host-location of wasps, and ultimately help the high-yield cultivation of F. awkeotsang.

爱玉子为引种自台湾的特种果树，由于爱玉子与其传粉小蜂为共生关系，小蜂的缺失必定造成爱玉子传粉链的断裂和传粉系统的损毁，而小蜂对寄主的准确定位是共生系统修复与维系的前提。已知花序释放的挥发物与传粉小蜂对其寄主的识别和定位紧密相关，但对二者之间相互作用的机制所知甚少。本项目将 1）调查爱玉子花序发育与挥发物释放之间的关联性，以及爱玉子不同雌、雄品系在不同生态地理环境下花序发育期的差异；2）利用动态实地采样法－气相色谱/质谱仪联用（GC/MS）技术，揭示花序所释放的挥发物成分的时空特异性；3）通过昆虫触角电位技术（EAG）和嗅觉选择行为测定实验，测试不同挥发物成分与传粉小蜂寄主选择行为之间的相关效应，从而揭示维持爱玉子－传粉小蜂共生关系的化学生态学机制，筛选出对传粉小蜂具有吸引作用的化学信息素配方，提高爱玉子传粉小蜂对其寄主的化学识别和定位效率，实现爱玉子高产栽培。

通过标记追踪观察福建莆田、浙江舟山和台湾高雄三地不同地理生态条件、不同品系的爱玉子和野生薜荔雌、雄花序和花发育过程，掌握了雌花期和雄花期的发生时期及时长，明确了栽培爱玉子的雄花期与雌花期之间的有效重叠期。.利用动态顶空吸附法和GC-MS分析，研究接受期以及传粉/产卵5天后爱玉子和薜荔雌/雄花序挥发物成分。结果表明：二者花序挥发物的组分复杂，种类繁多，主成分是对传粉蜂具显著吸引作用的芳樟醇。组成雌、雄花序的接受期挥发物信号的化合物种类与数量不同，但两者之间的共有化合物却占花序挥发物总量的50-70%，且接受期雌、雄花序挥发物组成比例相似，小蜂无法通过花序挥发物信号的差异，区别雌、雄花序。传粉/产卵前后花序挥发物信号发生变化，传粉小蜂通过接收榕果发出的化学信息，判断选择适合的寄主。.利用Y型嗅觉仪测定薜荔榕小蜂对薜荔和爱玉子雌花期榕果挥发物的行为反应。结果表明：（1）寄主榕果挥发物浓度影响传粉小蜂的寄主定位；（2）薜荔传粉小蜂对低浓度爱玉子雌花期雌/雄榕果挥发物、爱玉子传粉小蜂对低浓度薜荔雌花期雌/雄榕果挥发物均既无趋向也无驱避行为；薜荔传粉小蜂对高浓度的爱玉子雌花期雌/雄榕果挥发物表现为显著的驱避行为，而爱玉子传粉小蜂对高浓度薜荔雌/雄雌花期榕果挥发物表现为显著的趋向行为，因此，薜荔传粉小蜂与爱玉子传粉小蜂存在寄主专一性不对称现象，爱玉子传粉小蜂进入薜荔雌/雄果内传粉或产卵的可能性较大，而福州地区的薜荔传粉小蜂可能难以进入爱玉子雌/雄果内传粉或产卵。.依据雌花期榕果挥发物成分分析结果，应用Y型嗅觉仪检测爱玉/薜荔传粉蜂对38种单一信息化合物的行为反应，筛选出对传粉小蜂具有吸引作用的3种信息素：芳樟醇、苯甲醇和松油醇，进行正交实验筛选出最佳配方。信息素的田间应用显著提高了传粉蜂对寄主的定位效率，提高了爱玉子花序挂树率、单果雌花结实率、单果虫瘿形成率，爱玉子产量显著提高。