咖啡根系分泌物在根际的累积特征及其驱动根际微生物群落演替的研究

Coffee is an important economic crop in tropical region, which planting area in China has reached 130,000 hectares, and mainly in poverty-stricken areas of Yunnan, Hainan and other provinces. So, coffee plays an important role in increasing the income of farmers and promoting local economic development. At present, replanting is the first choice for the renewal of the old coffee garden, but replanting disease has become a serious problem for the sustainable development of the industry, which needs to be solved urgently. Previous studies have shown that the occurrence of coffee replanting is closely related to the soil microbial imbalance. But so far, the accumulation characteristics of root exudates in field environment and the mechanism of that affecting the succession of soil microbial community have not been well studied. Therefore, this study is to research the accumulation characteristics of root exudates in coffee rhizosphere soils under different health conditions by GC-MS, and field and pot experiments were conducted to study the effects of root exudates on rhizosphere microbial diversity by Illumina MiSeq high-throughput sequencing. The purpose of the study was to reveal the accumulation characteristics of root exudates in rhizosphere soil and to clarify the internal relation between succession of rhizosphere microbial community and root exudates. The results of the study are conducive to revealing the mechanism of coffee replantation from the perspective of rhizosphere microecology and providing theoretical basis for overcoming the coffee replantation disease, as well as, contribute to the sustainable development of the coffee industry.

咖啡是热区重要的经济作物，在我国种植面积已达13万公顷，主要种植于云南、海南等省份的“老少边穷”地区，对带动咖农脱贫致富和促进地方特色经济发展有显著成效。再植是目前咖啡老园更新的首选，但再植病已成为产业可持续发展亟待解决的严重问题。前期研究发现咖啡再植病的发生与土壤微生物菌群失衡密切相关。但至今，分泌物在大田生境中的积累规律及其对根际微生物菌群的影响机制尚不明确。因此，本研究拟通过GC-MS分析不同健康状态咖啡根际土中根系分泌物的积累特征；采用大田和盆栽试验，应用Illumina MiSeq高通量测序等技术研究根系分泌物对根际微生物多样性的影响，揭示咖啡根系分泌物在根际土中的累积特征，阐明根际微生物菌群演替与根系分泌物之间的内在联系。本项目的开展有助于从根际微生态角度揭示咖啡再植病产生的机理，将为克服咖啡再植病提供新思路和理论依据，有助于咖啡产业可持续发展。

咖啡是世界三大饮料之一，具有广泛的营养、经济和药用价值。咖啡是多年生经济作物，随其种植年限增加，产生了严重的再植病，已成为制约产业可持续发展的严重问题，亟待解决。前期研究发现咖啡再植病的发生与土壤微生物菌群失衡密切相关。但至今其内在的机制尚不明确。本项目采集海南澄迈、琼海和万宁代表性咖啡园不同健康状态咖啡植株根际土壤，应用LC-MS分析其根际土壤代谢特征，应用BIOLOG-ECO、Illumina MiSeq分析其土壤微生物多样性，并开展盆栽试验加以验证。研究表明：咖啡根际土壤存在严重的酸化现象，根际微生物多样性及其代谢活力均低于健康植株；包括4-乙基苯甲酸、对氨基苯甲酸等潜在化感物质在内的28种化学物质的相对含量在发病植株根际土壤中显著增加；相关性分析表明与土壤pH相比，根际土壤代谢物与根际微生物菌群相关性更高。盆栽试验表明随发病咖啡植株根际土水提液浓度的升高，咖啡幼苗生长发育受阻；根系表皮细胞变小，细胞壁及内膜系统逐渐被破坏，形成空腔；根系干鲜重、总根长、根体积、根尖数、总根表面积以及根系活力均逐渐下降；土壤微生物多样性整体上呈现出先下降后上升的变化趋势；微生物菌群结构发生显著变化，变化规律与其在不同健康状态咖啡植株根际土壤中的变化规律基本一致。综上，咖啡根系分泌物中存在自毒物质，抑制咖啡幼苗生长发育，影响土壤微生物多样性，介导土壤微生物菌群结构变化。本研究揭示了咖啡根系分泌物在根际土中的累积特征，及其与根际微生物菌群演替的内在联系，为克服咖啡再植障碍提供新思路和理论依据。

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