Background and aims

Overaccumulation of allelochemicals in soil from trees has a negative effect on the growth of Panax notoginseng and cause root rot. Many plant secreted phenols are water-soluble substances that can be depleted by leaching. However, comprehensive understanding of the effect of leaching of phenols in Chinese fir soil on P. notoginseng root rot disease is still lacking.

Methods

Soil with high level of phenols was leached with five intensities and their effect on the root rot of P. notoginseng was assessed. Then, the relationship of root rot with changes in soil chemical properties and phenol content as well as rhizospheric microorganisms was analyzed.

Results

With increasing leaching intensity, the levels of phenols in soils and the incidence of root rot decreased significantly. Decreased phenol content could alleviate root rot by modifying the soil microbial community. Network analysis showed that root rot incidence was positively correlated with the p-hydroxybenzoic acid-enriched pathogenic fungus Ilyonectria but negatively correlated with p-hydroxybenzoic acid (HA)-, ferulic acid (FA)- or vanillic acid (VA)-suppressed bacteria, including Sphingomonas, Lysobacter, Massilia and Burkholderia. Culture experiments confirmed that individual HA, FA and VA as well as a mixture of the five phenols with increasing concentrations could stimulate the growth and sporulation of I. destructans but suppress the growth and biofilm formation of bacteria (Burkholderia and Lysobacter). Moreover, Burkholderia isolates showed antagonistic activity against the growth of I. destructans.

Conclusions

Leaching could relieve the stimulation of pathogenic fungi by phenols and reduce the pressure on phenolic-suppressed bacteria, thereby reducing the incidence of root rot disease.

中文翻译：

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浸出通过改变土壤微生物群减轻三七中苯酚介导的根腐病

背景和目标

树木土壤中化感物质的过度积累会对三七的生长产生负面影响并导致根腐病。许多植物分泌的酚类是水溶性物质，可以通过浸出来消耗。然而，目前尚缺乏对杉木土壤酚类浸出对三七根腐病影响的综合认识。

方法

以五种强度浸出具有高水平酚类物质的土壤，并评估它们对三七根腐病的影响。然后，分析了根腐病与土壤化学性质和苯酚含量以及根际微生物变化的关系。

结果

随着淋溶强度的增加，土壤中酚类物质含量和根腐病发生率显着降低。降低苯酚含量可以通过改变土壤微生物群落来缓解根腐病。网络分析表明，根腐病发生率与富含对羟基苯甲酸的病原真菌Ilyonectria呈正相关，但与对羟基苯甲酸（HA）-、阿魏酸（FA）-或香草酸（VA）-抑制细菌呈负相关，包括鞘氨醇单胞菌、溶杆菌、马西利亚和伯克霍尔德菌. 培养实验证实，单独的 HA、FA 和 VA 以及浓度增加的五种酚的混合物可以刺激I. destructans的生长和孢子形成，但抑制细菌（伯克霍尔德氏菌和溶血杆菌）的生长和生物膜形成。此外，伯克霍尔德氏菌分离株显示出对抗破坏伊氏菌生长的拮抗活性。

结论

浸出可以减轻酚类对病原真菌的刺激，降低对酚类抑制菌的压力，从而减少根腐病的发生。