Avocado root rot, driven by soil-borne fungi such as Fusarium spp., poses a major challenge to global avocado production. The rhizosphere microbiome is critical for plant health, yet the impact of root rot on bacterial community structure and its implications for disease management remain poorly understood. Here, we combined culture-independent 16S rDNA amplicon sequencing with culture-dependent isolation to characterize bacterial communities in healthy and Fusarium-infested avocado bulk and rhizosphere soils. Key beneficial taxa, notably Bacillus, were then isolated and evaluated for their antagonistic potential. Results showed that root rot significantly reduced rhizosphere bacterial α-diversity, altered community structure, and depleted phyla such as Actinobacteriota and Firmicutes that contain beneficial taxa. Beneficial genera such as Bacillus and Streptomyces declined, while cultivable Fusarium counts increased. Negative correlations between Fusarium abundance, the bacteria-to-fungi ratio, and the relative abundance of beneficial bacteria further underscore their suppressive role. Guided by these findings, we isolated Bacillus strain NB92, identified as Bacillus siamensis through morphological, biochemical, and 16S rRNA and gyrA gene analyses. NB92 exhibited strong antagonistic activity against the root rot pathogen (Fusarium sp. St7) via both direct antagonism and volatile organic compound production. Inoculating NB92 into diseased rhizosphere soil boosted Bacillus counts and reduced Fusarium abundance. Moreover, NB92 effectively inhibited the pathogen’s necrotizing ability. B. siamensis NB92 thus represents a promising, sustainable biocontrol agent and contributes to the development of microbiome-based strategies for managing avocado root rot.

Soil salinity disrupts the balance of plant ions by promoting the accumulation of both Na+ and Cl− while simultaneously impairing the acquisition of

Background: The NAC family constitutes one of the largest families of plant-specific transcription factors and plays crucial roles in fruit development, ripening, seed life, and stress responses. However, comprehensive characterization of NAC genes in Persea americana (avocado), an economically important horticultural crop, has been largely unexplored. Methods: We performed a genome-wide identification and systematic characterization of NAC transcription factor (TF) genes in P. americana using blastp analysis, phylogenetic reconstruction, expression profiling and weighted gene co-expression network analysis (WGCNA). Results: A total of 130 NAC genes (PaNACs) were identified and distributed across all 12 chromosomes. Phylogenetic analysis classified these PaNACs into eight distinct subfamilies. WGCNA identified 43 co-expression modules, with 68 PaNAC genes distributed across 24 modules associated with hormone signaling, cell wall modification, secondary metabolism, and fatty acid beta-oxidation. Among 48,785 developmental differentially expressed genes (DEGs), 70 PaNAC genes were differentially expressed, with PaNAC003 and PaNAC002 showing the strongest upregulation and PaNAC023 and PaNAC025 the strongest downregulation. Among 9488 ethylene-responsive DEGs, PaNAC041 was suppressed by ethylene and induced by 1-methylcyclopropene (1-MCP, a competitive inhibitor of ethylene perception), while PaNAC016, PaNAC085, and PaNAC086 showed the opposite pattern. Conclusions: These findings provide a genomic and transcriptional framework for future functional investigation of PaNAC genes and their potential relevance to avocado fruit development and postharvest ripening.