Isolation and Identification of Pathogens Causing Rhododendron Wilt and Screening of Antagonistic Bacteria

doi:10.16409/j.cnki.2095-039x.2026.02.049

Abstract

Abstract: Rhododendron wilt significantly impairs the ornamental and economic value of the Bijie Hundred-Mile Rhododendron Nature Reserve. To minimize the risks of chemical control, this study aimed to identify the causal pathogen and screen endophytic bacteria with strong antagonistic activity against it, along with a preliminary investigation of their inhibitory mechanisms. Potential pathogenic fungi were isolated from diseased petals, and their pathogenicity was verified by Koch’s postulates. Antagonistic bacteria were isolated from adjacent healthy petal tissues and screened using the dual-culture plate assay; inhibition rates were calculated to evaluate efficacy. Based on morphological characteristics, ITS sequence phylogeny, and pathogenicity tests, the most virulent isolate MLR-1 was identified as Neopestalotiopsis clavispora. Among three antagonistic bacterial isolates obtained, Bacillus subtilis BST-1 exhibited the strongest inhibition, with a rate of 47.37% after 4 days of co-culture; the other two were identified as Bacillus altitudinis. The supernatants of these antagonists, even after heat treatment at 100 ℃ for 15 min, still significantly suppressed mycelial growth, indicating the presence of heat-stable bioactive compounds. This study identifies N. clavispora as the causal agent of Rhododendron wilt and demonstrates that B. subtilis BST-1 has promising biocontrol potential. The thermostable metabolites produced by this strain represent candidate agents for developing specialized biocontrol products, providing a theoretical basis for green management of this disease.

Key words: Rhododendron wilt, antagonistic bacteria, Neopestalotiopsis clavispora, petal-derived endophytes

CLC Number:

S476

LENG Chenxi, SHAN Fei, WANG Qian, ZHANG Ximin, TANG Jing. Isolation and Identification of Pathogens Causing Rhododendron Wilt and Screening of Antagonistic Bacteria[J]. Chinese Journal of Biological Control, 2026, 42(5): 1216-1227.

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