Beneficial rhizobacterium provides positive plant–soil feedback effects to Ageratina adenophora

doi:10.1016/S2095-3119(20)63234-8

摘要/Abstract

摘要：

根际微生物群落在促进或抑制外来物种的建立中起重要作用。入侵植物与土壤微生物群落(如根际细菌)的相互作用，会导致土壤微生物群落发生变化，因而影响外来植物与本地植物之间的竞争关系。紫茎泽兰是我国一种危害严重的外来入侵杂草。已有研究证实，紫茎泽兰入侵后会影响根际土壤微生物群落结构，并形成对它自身生长的正反馈效应，但这其中的内在机制还有待深入探究。前期调查发现，紫茎泽兰重度入侵地区的根际土壤中一种有益菌蜡样芽孢杆菌的含量明显高于轻度入侵地区的。因此，本研究从促进植物根际有益微生物增长及其反馈效应的角度，拟揭示紫茎泽兰入侵扩张的根际有益菌作用机制。研究比较了紫茎泽兰不同入侵程度土壤中蜡样芽孢杆菌的含量，检测了紫茎泽兰根系分泌物对蜡样芽孢杆菌生长和土壤特性的影响，还对比分析了蜡样芽孢杆菌处理对紫茎泽兰生长的反馈作用。结果表明：蜡样芽孢杆菌的含量随紫茎泽兰入侵程度的加深而明显增加，入侵土壤中的菌含量几乎达到了非入侵土壤的两倍。紫茎泽兰根系分泌物处理其根际土壤后，蜡样芽孢杆菌的含量在1天后随时间延长明显增加，最高达近两倍，且土壤营养成分含量也发生了明显变化，如铵态氮和有效磷含量相比于对照分别增加了41%和27%。土壤中添加蜡样芽孢杆菌不同程度地促进紫茎泽兰根际两种主要化感物质泽兰二酮和羟基泽兰酮的降解，其中泽兰二酮的浓度在处理后的48、72、96 h分别比灭菌土壤中的浓度低338%，356%和723%；并且在该处理的土壤中，紫茎泽兰的发芽率显著提高了50%，根长增加了117%，苗长增加了48%，鲜重增加了81%，而本地其他植物的生长变化不大。这些结果说明蜡样芽孢杆菌对紫茎泽兰生长具有偏利作用，同时可促进化感物质的降解以削弱紫茎泽兰的自毒作用，为根际聚集有益菌介导的外来植物入侵扩张的理论提供了科学依据。

Abstract:

Rhizosphere microbial communities play important roles in facilitating or inhibiting the establishment of exotic species. Since some invasive plants interact with soil microbial communities such as rhizosphere bacteria, changes triggered by rhizosphere bacteria may alter competitive interactions between exotic and native plants. This study compared the Bacillus cereus content in soils with different degrees of Ageratina adenophora invasion, and investigated the effects of A. adenophora allelochemicals on B. cereus growth and soil characteristics and the feedback effects of B. cereus on A. adenophora growth. Bacillus cereus content in the rhizosphere of A. adenophora increased with intensification of the invasion process, and newly invaded soil contained almost twice as much bacteria as noninvaded soil. When rhizosphere soil was added to the root exudates of A. adenophora, the contents of B. cereus were twice as much as the control, except on the first day. Certain soil parameters increased significantly, such as ammonium nitrogen (NH₄⁺-N) and available phosphorus (AP), which were increased by 41 and 27%, respectively. Soil treatment with B. cereus promoted the degradation of two allelochemicals from the rhizosphere of A. adenophora, amorpha-4,7(11)-dien-8-one and 6-hydroxy-5-isopropy1-3,8-dimethyl-4a,5,6,7,8,8a-hexahydraphthalen-2(1H)-one, to varying degrees; and increased the germination rate by 50%, root length by 117%, shoot length by 48% and fresh weight by 81% for A. adenophora compared to those of untreated soil. Our results confirmed that the invasion of A. adenophora will promote an increase of B. cereus, a beneficial rhizosphere bacterium, which in turn induces a positive feedback effect on A. adenophora.

Key words: Ageratina adenophora , Bacillus cereus , feedback , allelochemicals , root exudates

. [J]. Journal of Integrative Agriculture, 2021, 20(5): 1327-1335.

SUN Yuan-yuan, ZHANG Qiu-xin, ZHAO Yun-peng, DIAO Yue-hui, GUI Fu-rong, YANG Guo-qing. Beneficial rhizobacterium provides positive plant–soil feedback effects to Ageratina adenophora[J]. Journal of Integrative Agriculture, 2021, 20(5): 1327-1335.

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