Incidence of Crown and Root Rot in Rhododendron simsii Caused by Phytopythium vexans in China and Screening of Endophytic Bacteria for Biocontrol

作者：Zhuo Liu, Yang Sun, Zhuoma Yongcuo, Xiaorui Zhang, Guibin Wang, Yuhua Liu, Tingting Dai · 发表于：Microorganisms · 年份：2025 · DOI：10.3390/microorganisms13112417 · 被引用次数：4 · 研究领域：Plant Pathogens and Resistance、Plant Pathogens and Fungal Diseases、Plant Parasitism and Resistance

Azaleas (Ericaceae) are among the most diverse ornamental plants, celebrated for their cultural and economic significance. R. simsii has been extensively utilized in horticulture as a parent species for both “pot azalea” cultivars and various cultivars grown in the warmer regions of China. From 2021 to 2023, approximately 15% of R. simsii in nurseries situated in the Xuanwu District, Nanjing, exhibited symptoms of wilting and chlorosis. Investigations revealed that these symptoms were caused by a pathogen responsible for crown and root rot. Strains were isolated from the roots of affected plants. The morphology of the colonies was predominantly radial to stellate, characterized by intercalary and terminal hyphal swelling. The sporangia appeared spherical, pyriform, or ovoid with a single papillae. For accurate identification, the 28S rDNA gene (Large subunit, LSU), cytochrome oxidase subunit I (COXI), and cytochrome oxidase subunit II (COXII) genes were amplified through PCR and then sequenced. The species was identified as P. vexans after completing the phylogenetic analysis. Healthy R. simsii plants were infected with zoospores and developed symptoms similar to those of natural infection. Furthermore, the morphological characteristics of the isolates from the experimentally infected plants were similar to those of the original inoculated strains. This study identified P. vexans as the pathogen causing root rot in R. simsii. During the sampling process, several strains were ...