不同青苔发病程度下柑橘叶片营养及叶际生物特征分析

为探讨不同青苔发病程度下柑橘叶片矿质营养元素含量和叶表生物群落结构的变化特征之间的关系,本研究对重庆江津区李市和白沙两个不同地点柑橘果园中的W·默科特叶片青苔病发生程度按G0~G5分级并进行病情指数统计,测定各病情等级下叶片的氮(N)、磷(P)、钾(K)、钙(Ca)、镁(Mg)、锌(Zn)、铜(Cu)、铁(Fe)、锰(Mn)、硼(B)这10种矿质营养元素含量,同时利用高通量测序技术测定叶片叶际真核生物的群落组成、丰度、差异,分析了不同病情等级下叶际生物特征与营养之间的关系。结果表明:两样地的柑橘青苔发病程度和病情特征较为一致。李市和白沙两个果园W·默科特叶片青苔病病情等级均与P、Mg含量显著负相关,与K、Ca含量显著正相关。不同病情等级下叶际真核生物在属水平上存在明显差异,病情等级1下优势属是Heterochlorella、Sporidiobolus和Cladosporium,病情等级2下优势属是Heterochlorella、Symmetrospora和Microsporomyces,病情等级3下优势属是Heterochlorella、Cladosporium和Sporidiobolus,病情等级4下优势属是Heterochlorella、Cladosporium和Heveochlorella,病情等级5下优势属是Heterochlorella、Cladosporium和Microsporomyces;在种水平上,主要病原生物uncultured Apatococcus、Cladosporium herbarum、Heveochlorella hainangensis的相对丰度较高,且与病情等级呈极显著正相关关系。进一步分析显示,叶片中P、Fe、Mg、Mn、Cu、N含量与叶片生物群落结构之间关系密切,主要病原生物uncultured Apatococcus、Cladosporium herbarum与P含量极显著负相关,与Ca含量极显著正相关。综上所述,柑橘青苔病与叶片P和Ca两种元素关系最为密切,青苔病发生程度高低可直接影响叶片中P和Ca的含量。

Characteristics of nutrients and leaf surface organisms under different citrus moss severities

The aim of this study was to explore the relationship between the leaf nutrient elements and leaf surface community structure under different citrus moss degrees. In this study, we collected the leaves of W·murcott from two different citrus orchards in Jiangjin district of Chongqing for experiments. The degree of leaf moss was classified into G0-G5 and the disease index was counted. Also, the nutrient element content of nitrogen (N), phosphorus (P), potassium (K), calcium(Ca), magnesium(Mg), zinc(Zn), copper(Cu), iron(Fe), manganese(Mn), boron (B) in the leaves of each disease level was determined. High-throughput sequencing technology was utilized to explore the community composition, abundance, difference of phyllosphere eukaryotes under different disease levels. The results showed that both of the severity and characteristics of citrus moss in the two orchards were similar. The content of P was significantly negatively correlated with disease severities, the content of Mg was significantly negatively correlated with disease severities, and the content of Ca was significantly positively correlated with disease severities, the content of K was significantly positively correlated with disease severities. At the genus level, the dominants in G1 were Heterochlorella, Sporidiobolus and Cladosporium, the dominants in G2 were Heterochlorella, Symmetrospora and Microsporomyces, the dominants in G3 were Heterochlorella, Cladosporium and Sporidiobolus, the dominants in G4 were Heterochlorella, Cladosporium and Heveochlorella, and the dominants in G5 were Heterochlorella, Cladosporium and Microsporomyces. The relative abundance of uncultured Apatococcus, Cladosporium herbarum, Heveochlorella hainangensis on leaf surface were positively correlated with the disease levels. The content of P, Fe, Mg, Mn, Cu, N had a great influence on the structure of leaf biota species. The main pathogen uncultured Apatococcus, Cladosporium herbarum were negatively correlated with the content of P and they were positively correlated with Ca. Investigating relationship between mineral nutrient elements in citrus leaves and the eukaryotic community structure of leaf surface, we found the P content was significantly negatively correlated with citrus moss severities and the relative abundance of the major pathogens, the Ca content in the leaves were positively correlated with the citrus moss disease levels and the relative abundance of the main pathogens. In conclusion, citrus moss was most closely related to P and Ca in leaves, and the occurrence degree of citrus moss can directly affect the content of P and Ca in leaves.