荔枝对霜疫霉病抗性分子机制的研究

Peronophythora litchi Chen ex Ko is a serious pathogen, refering to litchi downy blight which causing a loss of fruit about 30-80%. The study on resistance mechanism provide the basis and foundation for breeding of resistant varieties, which is fundamental means of disease control. In the previous work, we established an identification system of resistance to the Phytophthora. By using this system, we screened 30 litchi germplasm resources and obstained two cultivars with high resistance (HR) and susceptible (HS) respectively. In addition, we sequenced the transcriptome of pathogen (Peronophythora litchi) and participated in the project of litchi genome sequencing. Based on these results, the gene expression profiles between high resistance and susceptible cultivars were analysed under different period by using RNA-seq technology. Taking the advantages of litchi genome and phytophthora transcriptome sequenceing, we will get the genes involved in pathological response and disease resistance. The main genes will be cloned and the functional annotation, verification of expression profile and function identification followed. Afterwards, a model about the molecular response to litchi Phytophthora infection will be drawed, revealing the molecular mechanism of litchi downy blight resistance. To take together these work will put a solid basis on breeding a broad-spectrum, efficient, and stable disease resistance litchi cultivars.

荔枝霜疫霉病是危害荔枝最严重的病害之一，可导致30-80%的产量损失。培育抗病品种是减轻病害的根本途径，研究抗病机制可为抗病育种提供基础和依据。本项目组前期建立了荔枝霜疫霉病抗性鉴定体系，并对30份主栽荔枝品种进行了抗性鉴定，获得高抗和高感品种各2个，而且完成了病原菌（荔枝霜疫霉菌）的转录组测序和参与完成了荔枝基因组测序。本项目将在此基础上，利用RNA-seq技术分析不同时期高抗和高感品种果实受霜疫霉菌侵染后的基因表达变化,结合霜疫霉菌转录组和荔枝基因组测序数据，挖掘荔枝参与霜疫霉病病理反应和抗病性的相关基因；并对关键抗性基因进行克隆、功能注释、时空表达分析和功能验证；构建荔枝响应霜疫霉菌侵染的分子途径，进而揭示荔枝抗霜疫霉病的分子机制，为培育荔枝广谱、高效和稳定的抗病品种奠定基础。

荔枝是重要的热带、亚热带果树，其产量和果实品质受霜疫霉病危害严重。明晰荔枝果实对霜疫霉病的抗性机制已成为绿色防控该病首要解决的关键科学问题。主要研究内容：1）继续对2个荔枝品种（‘黑叶’和‘桂味’）对霜疫霉病的抗性进行跟踪鉴定，进一步证实2个品种对霜疫霉的抗性表现稳定。2）在组织显微结构水平对抗、感病品种的果皮结构进行观察，发现抗性品种‘黑叶’相对感病品种‘桂味’果皮结构较紧实，吸附孢子囊较少。3）完成霜疫霉接种后抗、感病品种果皮的转录组测序，并对响应霜疫霉菌侵染和抗、感病品种间表达差异的基因进行分析。抗病品种‘黑叶’响应霜疫霉表达基因（表达量差异1倍以上，FDR值小于0.001）共有1458个；感病品种‘桂味’共有1956个。抗性品种响应霜疫霉侵染的基因数目显著小于感病品种。抗、感品种接种霜疫霉后差异表达基因共1102个，对其进行pathway富集分析发现，抗、感病品种在苯丙酸生物合成、类黄酮生物合成、半乳糖代谢和植物激素信号转导途径的相关基因存在显著差异表达。4）对部分关键抗性相关候选基因的qRT-PCR验证，证实转录组分析的基因表达结果准确。5）对抗、感病品种抗性相关生理指标进行测量。结果表明，感病品种‘桂味’对霜疫霉侵染的生理响应更加明显。6）完成霜疫霉菌转录组测序，在霜疫霉菌中鉴定了一批致病相关基因，并构建系统进化树，在分子水平上确立了霜疫霉菌分类上属于腐霉科疫霉属。本项目在建立完善抗性鉴定体系的基础上，对抗病品种和感病品种霜疫霉病抗性进行跟踪鉴定，并从组织、生理和分子水平多角度探究荔枝对霜疫霉病抗性的分子机制，研究结果为开展荔枝相关抗性基因的表达调控奠定了基础。