Soil Attributes Modulate the Fungal Population and Diversity of Phytopathogens and Biocontrol Agents

Assam, along with other Northeast (NE) Indian states, is a pesticide-free zone, which increases the risk of pathogen infiltration to the fields from the surrounding biodiversity hotspot region. To identify potential phytopathogens and beneficial microbes (BCs) from these regions, we investigated the fungal diversity collected from eight districts in Assam. The fungal population in the clay-textured soil ranged from 4.27 to 4.83 × 10⁴ CFUgm⁻¹ soil. A total of 449 fungi were isolated, 437 were morphologically characterized, and 70 isolates showing macroscopic and microscopic variations were identified using ITS sequencing. Based on ITS sequences, the fungi belonged to 3 phyla, including Ascomycota (60), Basidiomycota (4), and Zygomycota (6), which were dispersed in 7 classes and 28 genera, and 12 isolates remained uncharacterized. Among the identified isolates, the known plant pathogens and mycotoxin producers included Fusarium, Curvularia, Penicillium, and Aspergillus, while BC included Trichoderma. Pearson correlation studies revealed that the fungal population was greatly affected by the soil pH and EC. Comprehensive studies using PCA plot indicates that soil EC promotes the evenness of fungal diversity. Moreover, the soil organic carbon alters the soil pH, which interacts with available nitrogen in the soil and consequently improves the fungal diversity. The finding concluded that the soil attributes, viz., organic carbon, available nitrogen, soil pH, and soil EC impacted heterogeneous microbial populations and fungal diversity. We also report status of soil Cd, Cr, As, and mineral nutrients. Soil As ranged from 3.48 to 9.09 mg kg⁻¹. Equilibrium between biocontrols and phytopathogens among the isolated fungal population was observed.