Screening and biological characteristics of biocontrol endophytes against Idesia polycarpa stem canker

Stem rot of Idesia polycarpa Maxim., caused by Botryosphaeria dothidea, induces cankers that lead to tree death, severely affecting tree growth and fruit yield, and constraining the development of the I. polycarpa industry. This study aimed to screen for endophytes antagonistic to the stem rot pathogen from healthy trees of the cultivar 'Yuji' I. polycarpa and to investigate their biological characteristics, in order to provide a basis for biological management of the disease. A total of 105 endophytic fungal strains and 74 bacterial strains were isolated and purified from healthy I. polycarpa trees. Following screening by the plate confrontation method, the isolates were analyzed and identified via ITS and 16S rRNA sequencing. The biological characteristics of the selected biocontrol strain were further investigated.The biocontrol endophytic strain B47 was obtained. It shared 97.58%-97.83% sequence similarity with known species of the genus Aneurinibacillus and was named Aneurinibacillus sp. B47. This strain exhibited an inhibition rate of 84.56% against B. dothidea and a relative control efficacy of 44.44% on two‑year‑old I. polycarpa plants. It could grow and reproduce normally at temperatures of 5-50°C, pH 3-10, and salinity below 7%. It was an aerobic, catalase‑positive bacterium with strong growth potential.Aneurinibacillus sp. B47 exhibited strong antagonistic activity, broad environmental adaptability, and rapid growth, indicating its potential for development as a biocontrol agent against stem rot of Idesia polycarpa Maxim.