Plum Fruit Isolate Shows Strong Biocontrol Potential Against Brown-Spot Disease

Brown spot disease of European plum (Prunus domestica L.), caused by the fungal pathogen Alternaria alternata, seriously affects fruit yield and quality. A new laboratory study from Xinjiang, China, reports that a bacterial strain isolated from diseased plum fruit can suppress this pathogen with an effectiveness approaching that of a chemical fungicide in detached fruit assays, positioning it as a candidate for biological disease management.

The research team collected 1,000 diseased plum fruit samples from orchards in Kashi City and the counties of Jiashi, Shache, Maigaiti, and Yingjisha. From these samples, they isolated 210 antagonistic bacterial strains and screened them for antifungal activity using the plate confrontation method. One strain, designated XMAB21, showed the strongest activity among all tested isolates, inhibiting A. alternata growth at a rate of 81.2 percent. Identification work based on morphological characteristics, physiological and biochemical features, and 16S rDNA sequence analysis assigned XMAB21 to the species Bacillus velezensis.

The researchers then examined the strain’s sterile fermentation filtrate, which significantly inhibited the pathogen’s mycelial growth and spore germination, with inhibition rates of 57.22 percent and 87.56 percent, respectively. The filtrate also caused clear morphological changes in both hyphae and spores of the pathogen. Notably, the antifungal activity proved heat-stable: after treatment at 95 °C for 30 minutes, the filtrate still retained 62.49 percent of its inhibitory activity.

In detached fruit assays, treatment with XMAB21 fermentation broth reduced the lesion area on infected plums to 76.8 mm² and achieved a control efficacy of 89.07 percent. That performance was comparable to chlorothalonil, which reached 90.15 percent in the same assay. Beyond its activity against the plum pathogen, XMAB21 displayed broad-spectrum antifungal activity against ten plant pathogenic fungi, with inhibition rates ranging from 67.04 percent to 85.89 percent, although these measurements were made in vitro rather than on infected plants.

The study also documented multiple plant growth-promoting traits in XMAB21, including phosphorus solubilization, nitrogen fixation, siderophore production, secretion of protease, cellulase, and amylase, and indole-3-acetic acid (IAA) synthesis. Taken together, these findings indicate that B. velezensis XMAB21 combines direct pathogen suppression with growth-promoting functions in a single strain. The researchers conclude that XMAB21 has good potential as a biocontrol agent for managing brown spot disease in European plum. However, the reported control efficacy comes from detached fruit assays under laboratory conditions, and the strain’s performance in orchard field trials remains to be demonstrated before its practical value for growers can be confirmed.

Subject of Research: Study on the biocontrol effectiveness of Bacillus velezensis XMAB21 against Alternaria alternata induced brown-spot disease in European plum (Prunus domestica L.)

Article Title: Study on the biocontrol effectiveness of Bacillus velezensis XMAB21 against Alternaria alternata induced brown-spot disease in European plum (Prunus domestica L.)

Article References: Xie, P., Zhang, Y., Han, Q., Li, H., Gao, W., Xu, L., Fu, C., & Sha, S. (2026). Study on the biocontrol effectiveness of Bacillus velezensis XMAB21 against Alternaria alternata induced brown-spot disease in European plum (Prunus domestica L.). 3 Biotech, 16(11), Article 480. https://doi.org/10.1007/s13205-026-04904-x

Image Credits: AI Generated

DOI: 10.1007/s13205-026-04904-x

Keywords: biocontrol, effectiveness, Bacillus, velezensis, XMAB21, against, Alternaria, alternata, induced, brown-spot, disease, European