Li Bo, Wang Yanan, Hu Tongle, Qiu Dewen, Francis Frédéric, Wang Shuangchao, Wang Shutong
State Key Laboratory of North China Crop Improvement and Regulation, College of Plant Protection, Hebei Agricultural University, Baoding, China.
Department of Functional and Evolutionary Entomology, Gembloux Agro-Bio Tech, University of Liège, Gembloux, Belgium.
Front Plant Sci. 2022 Jul 15;13:937414. doi: 10.3389/fpls.2022.937414. eCollection 2022.
The citrus orchards in southern China are widely threatened by low soil pH and Huanglongbing (HLB) prevalence. Notably, the lime application has been used to optimize soil pH, which is propitious to maintain root health and enhance HLB tolerance of citrus; however, little is known about the interactive effects of soil acidity on the soil properties and root-associated (rhizoplane and endosphere) microbial community of HLB-infected citrus orchard. In this study, the differences in microbial community structures and functions between the acidified and amended soils in the Gannan citrus orchard were investigated, which may represent the response of the host-associated microbiome in diseased roots and rhizoplane to dynamic soil acidity. Our findings demonstrated that the severity of soil acidification and aluminum toxicity was mitigated after soil improvement, accompanied by the increase in root activity and the decrease of HLB pathogen concentration in citrus roots. Additionally, the Illumina sequencing-based community analysis showed that the application of soil amendment enriched functional categories involved in host-microbe interactions and nitrogen and sulfur metabolisms in the HLB-infected citrus rhizoplane; and it also strongly altered root endophytic microbial community diversity and structure, which represented by the enrichment of beneficial microorganisms in diseased roots. These changes in rhizoplane-enriched functional properties and microbial composition may subsequently benefit the plant's health and tolerance to HLB disease. Overall, this study advances our understanding of the important role of root-associated microbiota changes and ecological factors, such as soil acidity, in delaying and alleviating HLB disease.
中国南方的柑橘园受到土壤pH值低和黄龙病（HLB）流行的广泛威胁。值得注意的是，施用石灰已被用于优化土壤pH值，这有利于维持根系健康并提高柑橘对HLB的耐受性；然而，关于土壤酸度对HLB感染的柑橘园土壤性质和根际（根表和内生菌）微生物群落的交互作用知之甚少。在本研究中，调查了赣南柑橘园酸化土壤和改良土壤之间微生物群落结构和功能的差异，这可能代表了患病根系和根表中宿主相关微生物群对动态土壤酸度的响应。我们的研究结果表明，土壤改良后土壤酸化和铝毒性的严重程度得到缓解，同时柑橘根系的根活性增加，HLB病原体浓度降低。此外，基于Illumina测序的群落分析表明，土壤改良剂的施用丰富了HLB感染的柑橘根表中与宿主-微生物相互作用以及氮和硫代谢相关的功能类别；它还强烈改变了根内生微生物群落的多样性和结构，表现为患病根系中有益微生物的富集。根表富集的功能特性和微生物组成的这些变化可能随后有利于植物的健康和对HLB病的耐受性。总体而言，本研究增进了我们对根相关微生物群变化和生态因素（如土壤酸度）在延缓和减轻HLB病方面重要作用的理解。
