磷水平对内生真菌枫香拟茎点霉与水稻互作平衡的调控作用

Regulation of Phosphorus Levels on the Interaction Balance between Endophytic Fungus Phomopsis liquidambaris and Rice

内生真菌枫香拟茎点霉(Phomopsis liquidambaris,B3)能够与水稻建立互惠互利关系,但是两者之间的互作关系是否会受到土壤中有效磷含量的影响尚不清楚。本研究以水稻-B3共生体系为研究对象,在低磷(LP)、中磷(MP)、高磷(HP)三个磷水平中分别设置未接菌组(E-)、接菌组(E+),共六个处理,探讨在室外盆栽试验与温室试验下,不同磷水平对植物-内生真菌互作关系的影响。室外盆栽试验表明,在低磷水平下,接种B3显著促进水稻生长,水稻产量提高7.05%;在中高磷水平下B3对水稻生长的作用减弱。为排除土壤中复杂环境的影响,设计温室试验,结果表明,在低磷水平下,与未接种处理相比,接种B3的水稻根冠比提高22.48%,磷含量增加39.98%,同时,B3显著增强叶绿素的含量以及水稻根部蔗糖、葡萄糖、果糖积累量,然而,低磷环境会限制B3在水稻根部的定殖量;在中磷和高磷水平下,B3定殖量高但对水稻的促生作用减弱。以上结果表明,在低磷水平下,B3与水稻之间是低丰度互作平衡关系,在该条件下,B3在水稻根部的定殖量低但能显著促进水稻生长;而在中高磷水平下,B3与水稻是高丰度互作平衡关系,B3在水稻根部定殖量高,虽然没有促生作用但可能具有其他优势。本研究有利于解释磷是否以及如何影响内生真菌与水稻的互作关系。

【Objective】The interaction between endophytic fungi and plants is affected by many factors,among which the content of phosphorus in soil plays a key role in regulating the interaction between them.However,it is not clear whether and how phosphorus fertilizer in the environment affects the interaction between endophytic fungi and plants.【Method】In this study,the symbiont of Phomopsis liquidambaris(B3)and rice(Oryza sativa L.)was used as the experimental model.Three different phosphorus levels,i.e.,low phosphorus(LP),medium phosphorus(MP),high phosphorus(HP),uninoculated endophytes treatment(E-),and inoculation endophytes treatment(E+)were designed in this experiment.Physiological indexes of rice and B3 colonization were detected under different phosphorus levels to explore how phosphorus regulates the interaction between B3 and rice in the outdoor experiment and greenhouse experiment.【Result】In the outdoor experiment,B3 significantly(i)increased the phosphorus uptake ability of rice,(ii)promoted rice growth in the whole growth period and the formation of rice grain in the mature stage,and(iii)increased the rice yield by 7.05%under LP treatment.In MP and HP treatments,the effect of B3 was weakened.In the greenhouse experiment,under LP treatment,compared with the uninoculated treatment,the root/shoot ratio of rice inoculated with B3 increased by 22.48%,and resulted in an enhanced phosphorus uptake ability of rice by 39.98%.There was a significant enhancement of photosynthesis in rice and the accumulation of carbon sources such as sucrose,glucose and fructose in rice roots.However,the colonization of B3 was significantly limited under this condition.Also,consistent with this result,the biomass of B3 cultured in the LP medium was significantly lower than that in MP and HP mediums,which meant that B3 would be significantly affected by the phosphorus concentration.In the MP and HP treatments,B3 had high colonization in rice roots,but had little effect on rice growth.【Conclusion】Phosphorus concentration affects the symbiotic relationship between B3 and rice.In LP treatment,B3 colonization was low in rice roots,but it significantly promoted plant growth.In MP and HP treatments,B3 had high colonization rates in rice roots but with no significant effect on rice growth.Understanding the influence of phosphorus fertilizer on the interaction between endophytic fungi and plants will be helpful to improve the utilization efficiency of phosphorus fertilizer and microbial resources,which will provide a new path for the sustainable development of agriculture.