Isolation and Identification of the Dominant Pathogen of Salvia miltiorrhiza Root Rot and Observation of Its Infection Process in S.miltiorrhiza Roots

WANG Fei; YANG Jin; ZHAO Ying; LI Shaojian; LI Xuemeng; QIN Yanhong; GAO Suxia; LU Shuhao; SHEN Danyu; QI Hongzhi

doi:10.15933/j.cnki.1004-3268.2025.12.011

Abstract：To identify the dominant pathogen causing Salvia miltiorrhiza root rot in Henan Province and clarify its infection process,diseased root samples were collected from three main producing areas(Yuzhou City,Mianchi County,and Fangcheng County)in Henan Province.The dominant pathogens were identified based on morphological characteristics and molecular biological analyses.Highly pathogenic isolates were screened through pathogenicity assays.The infection process of a selected isolate in S.miltiorrhiza roots was observed using green fluorescent protein(GFP)labeling and fluorescence microscopy.The results showed that Fusarium oxysporum exhibited the highest isolation frequencies(63.16%,48.28%,and 39.63%,respectively)among pathogens isolated from the three areas,indicating it as the dominant pathogen of S.miltiorrhiza root rot in Henan Province.Following inoculation of S.miltiorrhiza seedlings with F.oxysporum spore suspension:spores adhered to the root surface and began to germinate at 12 h post-inoculation(hpi);germinated spores developed into hyphae,which spread along the intercellular spaces of epidermal cells between 24-48 hpi;hyphae expanded into the cortex and extended along parenchyma cells,eventually surrounding entire cells by 3-5 days post-inoculation(dpi);extensive hyphal networks formed randomly within cortical cells by 7-9 dpi;hyphae surrounded the entire root cortex and extended to the root tip by 11 dpi;all root cells were infected by 14 dpi.At this stage(14 dpi),the stem base turned brown,fibrous roots became brittle and easily broken,and root tips of some plants turned yellow.In conclusion,F.oxysporum is the dominant pathogen causing S.miltiorrhiza root rot in Henan Province.This study elucidated the infection process of GFP-labeled F.oxysporum in S.miltiorrhiza roots from a histopathological perspective,providing a basis for targeted control strategies against this disease.