Diversity of Antifungal Properties in Bacterial Isolates from Different Plant Species Growing Across Uzbekistan

Abstract

Plant-associated bacteria play a crucial role in protecting plants from pathogens, yet the diversity and antagonistic potential of these bacteria across different plant species remain underexplored, especially in central Asia. To investigate the competitive dynamics between phytopathogenic fungi and plant-associated bacteria, we collected stem and root samples from 50 plant species across nine regions of Uzbekistan. A total of 3355 bacterial isolates were obtained (1896 from roots and 1459 from shoots) and screened for antifungal activity against six fungal pathogens, resulting in 432 antagonistic isolates. These were identified through 16S rDNA sequencing, revealing 65 bacterial species across three phyla: Firmicutes, Proteobacteria, and Actinobacteria, predominantly in the respective families Bacillaceae, Pseudomonadaceae, and Caryophanaceae. The plant Salsola vvedenskii hosted the highest diversity of antagonists (26 species), while other species harbored fewer. Plant species showed strong associations with specific bacterial communities, with 14 plant species each hosting unique antagonists. Enzymatic profiling revealed functional diversity, with Bacillus species producing protease, cellulase, and lipase activities, while Pseudomonas species excelled in xylanase, glucanase, and cellobiase production. B. mojavensis 9r-29 stood out by producing all six enzymes. These findings underscore the ecological diversity and biocontrol potential of plant-associated bacteria in natural ecosystems, offering promising candidates for sustainable plant protection strategies.

Keywords: antagonistic bacteria; antifungal activity; biocontrol; enzymatic activities; plant pathogens.

Figure 1

Research strategy for endophytic molecular biodiversity.

Figure 2

Overview of plant diversity collected from nine regions of Uzbekistan. (a) Map of the Republic of Uzbekistan with locations marked for plant sample collection. (b) Diversity of plant species categorized by family and genus. (c) Distribution of plant species by family and genus.

Figure 3

Antifungal Activity of Bacterial Isolates from Plant Species. (a) Examples of bacterial isolates exhibiting antifungal activity against various phytopathogenic fungi. (b) Heatmap illustrating the antifungal activity of these isolates against six different phytopathogenic fungi. The ‘No’ indicates the number of bacterial isolates capable of inhibiting each pathogenic fungus.

Figure 4

Phylogenic relationship of antagonistic bacteria isolated from plant species. The circular map depicts bacterial phyla and family taxonomic units. The evolutionary history was inferred by using the maximum likelihood method and Tamura–Nei model. The tree with the highest log likelihood (−15,874.16) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches.

Figure 5

Bacterial count distribution by plant species.

Figure 6

Distribution of antagonistic bacteria by plant species and plant parts. (a) The distribution of antagonistic bacterial isolates was analyzed according to the plant species and specific plant parts (roots, shoot) from which they were obtained. (b) The data show the distribution of bacterial antagonists based on the number of plant hosts.

Figure 7

Enzymatic activities of the antagonistic bacteria. Protease, lipase, cellulase, xylanase, glucanase, and cellobiase activities were assessed in antagonistic bacterial isolates. Symbols ‘+’, ‘++’, and ‘+++’ indicate low, moderate, and high levels of enzymatic activity, respectively, while ‘−’ denotes the absence of activity.