植物内生真菌缓解连作花生早衰及促进籽粒形成的机理

Peanut is an important oil crop of China, which is widely cultivated in the hilly red soil region of southern China. Peanut early senescence induced by continuous cropping is an important reason for peanut production decline in red soil area. Our previous study showed that the application of fungal endophyte Phomopsis liquidambari strain B3 could effectively delay peanut early senescence and promote kernel production, but the underlying mechanisms are still unknown. Herein, we hypothesis that fungal endophyte application enhances photosynthesis and nodulation and N2-fixation ability, stimulates arbuscular mycorrhizal formation, enhances drought resistance capacity, assists plant to absorb water and mineral substances, and ultimately delays peanut early leaf abscission and increases peanut production. In order to verify our hypothesis, we will determine the effects of P. liquidambari on photosynthesis and carbohydrate partitioning, plant drought parameters, development of arbuscular mycorrhiza and mineral nutrients uptake in the later stage of peanut cultivation. Meanwhile, we will combine plant physiological status determination and transcriptome, proteome and differential gene expression analysis to explore the effects of P. liquidambari on plant disease resistance genes expression. Furthermore, we will prove that fungal endophyte, rhizobia and arbuscular mycorrhizal fungi enable more carbohydrate allocate to root without causing early leaf nutrient starvation, delaying peanut early senescence and simultaneously extending the growth period and providing adequate nutrient and water to increase peanut production. Our study will provide technical support for the delay of peanut early senescence, and also provide theoretical reference for the delay of early senescence and promotion of production of other crop plants.

花生是我国重要油料作物，南方红壤区是主要产区之一。连作导致的早衰是红壤区花生低产的重要原因。前期研究表明，施加植物内生真菌枫香拟茎点霉B3菌株，可以有效缓解连作导致的早衰并促进籽粒形成，其机理不清楚。我们提出假说认为，内生真菌促进花生光合作用和结瘤固氮，促进丛枝菌根形成、促进抗旱和矿质元素与水分吸收，诱导抗病，最终使叶片养分充足而减缓脱落，缓解了早衰。为验证上述假说，我们拟分析花生生育后期光合作用和养分分配，分析植物抗旱指标，探讨丛枝菌根发育状况对水分与矿质元素吸收的影响，分析抗病生理指标，用转录组和蛋白质组分析的方法，探讨花生诱导抗病的基因表达。试图证明内生真菌、根瘤菌和丛枝菌根真菌共同作用，导致花生生育后期养分向荚果输送不会导致叶片养分的亏缺，缓解了早衰，同时有效生育期长，且籽粒获得养分和水分充足导致高产。希望为花生早衰的缓解提供技术支持，也为其他作物克服早衰，增加产量提供理论参考。

花生是我国重要油料作物，南方红壤区是主要产区之一。连作导致的早衰是红壤区花生低产的重要原因。前期研究表明，施加植物内生真菌枫香拟茎点霉B3菌株，可以有效缓解连作导致的早衰并促进籽粒形成，其机理不清楚。本项目从三方面开展研究。首先，B3菌株接种提高花生光合速率，改善植物氮营养状况。接种组光合速率提高，根部蔗糖和可溶性糖含量增加；植株全氮和可溶性蛋白含量提高。接种处理显著降低了叶绿素的降解、膜离子泄露水平和衰老相关基因的表达，同时提高了叶片的抗氧化能力。B3对连作花生结瘤固氮的促进作用，与其促进同化物向地下转运从而增加地下部分碳积累有关。B3菌丝可作为慢生根瘤菌趋向根系的通道与营养供应者，菌丝分泌的黄酮类物质有结瘤信号预启动的作用。B3接种组的花生根系分泌物也有利于固氮菌富集、结瘤基因表达。其次，B3接种提高了花生根内巨孢囊霉属的定殖，促进宿主抗旱。B3和珠状巨孢囊霉之间的协同互作提高了宿主抗旱能力和叶部钾含量。由该AMF产生的易提取-球囊霉素土壤相关蛋白（E-GRSP）显著累积于植物根围，和抗旱有关。在营养缺乏的情况下，B3能够显著促进植物对磷、铁的吸收。第三，B3接种促进花生抗病。预接种B3对花生苗期根腐病和成熟期叶斑病的相对防治效果分别达56.67%和61.73%。处理组增强了花生根部胼胝质沉积和细胞木质化程度；提高了抗氧化酶活性；促进了植物抗毒素如白藜芦醇苷、槲皮素的积累。B3使植物形成诱导系统性抗性，相关防御基因的转录水平提高。B3定殖花生后产生的根系分泌物能显著增加连作花生根际细菌的丰度与多样性，有利于抗病。本研究可为花生早衰的缓解提供参考。总体上按期完成了研究工作，实现预期目标。目前已经发表18篇研究论文，含SCI论文17篇，中文论文1篇。另有2篇SCI论文被录用并在线发表，申请发明专利1件。博士生3人，硕士生4人参加本项目研究并撰写相关学位论文，获得相应学位。