浒苔寡糖诱导采后荔枝果实对Peronophythora litchii的抗病生理机制研究

Fruit decay caused by Peronophythora litchii severely leads to great economic loss. Marine-derived oligosaccharide bio-preservatives have attracted much attentions. The studies on the inhibition of pathogens and the mechanism of disease resistance induction of harvested litchi fruit by oligosaccharides haven't been clearly reported yet. In our previous study, the Enteromorpha prolifera oligosaccharide (EPO) with clear structure was proved to decrease the disease index and maintain good quality of harvested litchi fruit. Based on the result of previous study, the relationship between disease resistance induced by EPO and changes in energy status, changes in respiratory metabolic pathways, changes in integrity of cell membrane of harvested litchi fruits will be analyzed through physiology and pathology techniques. The effects of EPO on energy status and respiratory metabolic pathways in litchi fruits will be determined, the role of energy status and respiratory metabolic pathways in the control of infection in harvested litchi fruit will be revealed, the mechanism of disease resistance improvement and the storage quality maintenance of harvested litchi fruits will be elucidated. This study are expected to gain new theories on the possible mechanism of oligosaccharides in inducing fruit disease resistance, and provide important scientific basis for improving the disease resistance, prolonging the shelf-life and developing novel marine biological preservatives.

荔枝霜疫霉菌侵染引起采后荔枝果实腐烂变质，造成巨大经济损失，海洋源寡糖类生物抑菌保鲜剂成为当前关注和研究热点。绿藻浒苔寡糖在采后荔枝病原微生物抑制及抗病性诱导机制方面的研究尚未见报道。本项目在前期已证实的浒苔寡糖结构明确并对采后荔枝果实抗病性研究取得阶段性成果的基础上，通过采后生理与病理学技术，分析浒苔寡糖诱导采后荔枝果实抗病性与组织能量状态变化、呼吸代谢途径变化、细胞膜结构及功能完整性变化等生理代谢之间的关系，明确浒苔寡糖对荔枝果实能荷水平及呼吸代谢途径变化的影响，揭示能荷水平与呼吸代谢途径变化在浒苔寡糖控制采后荔枝霜疫霉菌侵染中的作用机制，阐明浒苔寡糖提高采后荔枝果实抗病性与保持果实贮藏品质的机理。研究成果可望在寡糖诱导采后果实抗病性的可能机制方面获得新理论，为提高采后荔枝果实抗病性、延长果实保鲜期及开发海洋源采后生物保鲜剂提供重要科学依据。

研究发现，与接种P. litchii的荔枝果实相比，浒苔寡糖处理能够保持果实较高的果皮木质素含量及抗病物质相关酶活性，从而增强荔枝果实的抗病性，控制荔枝果实病害发生；此外，浒苔寡糖处理导致接种P. litchii的荔枝果实磷酸戊糖（PPP）途径增强，糖酵解（EMP）-三羧酸循环（TCA）削弱，荔枝果实抗病性增强；同时，浒苔寡糖处理有效延缓P. litchii侵染的荔枝果实果皮ATP、ADP含量和能荷水平的下降，使果皮的质膜、液泡膜、线粒体膜上ATPase活性始终处于较高水平，从而较好的维持细胞膜内外离子平衡及渗透压的稳定，进而保持果皮细胞膜结构和功能的完整性，维持较高抗病能力，延缓荔枝果实病害发生；研究还发现浒苔寡糖处理能够保持果实较好的贮藏特性和果实品质。研究成果为提高采后荔枝果实抗病性及开发海洋源采后生物保鲜剂提供一定理论基础。