Citrus cultivation has socioeconomic relevance, and gummosis Phytophthora diseases considerably reduce its yield. This infection has motivated the development of diagnostic procedures in the Citrus-Phytophthora pathosystem to assist breeding programs in selecting resistant rootstocks. The objective of this study was to standardize a method for detecting nuclei Phytophthora sp. for study the colonization process and the life cycle of the pathogen in infected stems of Rangpur lime rootstocks using flow cytometry. The stems were inoculated with a Phytophthora sp. isolated from a citrus population of Bom Jesus da Lapa, Bahia, Brazil. Firstly, the DNA ploidy level and nuclear genome size were determined from the mycelium cells of Phytophthora sp. and leaf cells of Rangpur lime, using the saline extraction buffer, procedure of preparation of suspensions in two stages (isolation and staining), with centrifugation of the nuclei suspensions and discard of the supernatant. The mean number of 1C (gametangia) and 2C (other tissues) Phytophthora sp. nuclei in Rangpur lime was estimated based on the reference values relative to the position of G₀/G₁ peaks of the 2C nuclei of Phytophthora sp. and of the Rangpur lime rootstock and based on the standardization of the amount of infected tissue, and the volume of nuclear suspension analyzed. In infected Rangpur lime, there is a higher mean number of 2C nuclei of Phytophthora sp., which correspond to hyphae in the vegetative growth stage, dispersion spores, and infection structures of the pathogen’s life cycle. On the other hand, 1C nuclei, in smaller quantities, correspond to gametangia. Therefore, the established flow cytometry procedure was reproducible and relatively fast for study the colonization process and the life cycle of the Phytophthora sp. on diseased plants of Rangpur lime.

柑橘种植具有社会经济相关性，而胶质疫霉病会大大降低其产量。这种感染推动了柑橘疫霉病系统诊断程序的发展，以协助育种计划选择抗性砧木。本研究的目的是标准化检测疫霉属菌核的方法。用于使用流式细胞术研究 Rangpur 石灰砧木受感染茎中病原体的定植过程和生命周期。茎用疫霉属菌种接种。从巴西巴伊亚州 Bom Jesus da Lapa 的柑橘种群中分离出来。首先，DNA倍性水平和核基因组大小是从菌丝体细胞中确定的。疫霉属 和 Rangpur 石灰叶细胞，使用盐水提取缓冲液，分两个阶段（分离和染色）制备悬浮液，离心细胞核悬浮液并丢弃上清液。1C (gametangia) 和 2C (其他组织) Phytophthora sp.的平均数量。Rangpur 石灰中的细胞核是根据相对于疫霉属物种 2C 细胞核的G ₀ /G ₁峰位置的参考值来估计的。和 Rangpur 石灰砧木，并基于受感染组织数量的标准化，以及分析的核悬浮液体积。在受感染的 Rangpur 石灰中，疫霉属的 2C 核的平均数量更高sp.，对应于营养生长阶段的菌丝、散布孢子和病原体生命周期的感染结构。另一方面，数量较少的 1C 核对应于配子体。因此，已建立的流式细胞术程序可重复且相对较快，可用于研究疫霉属的定植过程和生命周期。在 Rangpur 石灰的病株上。