Microbial Population Dynamics in Rhizosphere Soils of Healthy and Wilt-affected Pigeonpea Fields in Vikarabad District, Telangana, India

Abstract

Background: Soil microorganisms inhabiting the plant rhizosphere play a crucial role in maintaining soil health and suppressing soil-borne pathogens. Fusarium wilt, caused by Fusarium udum Butler, is one of the most destructive diseases of pigeonpea (Cajanus cajan [L.] Millsp.) in Telangana. However, information on the influence of wilt incidence on culturable rhizosphere microbial populations under field conditions is limited. Aims: This study aims to compare the culturable bacterial and fungal populations in the rhizosphere of healthy and wilt-affected pigeonpea fields across major pigeonpea-growing villages of Vikarabad district, Telangana, India. Methodology: A field survey was conducted during the 2025–26 cropping season in 60 villages. Paired rhizosphere soil samples were collected from healthy and wilt-affected pigeonpea fields. Bacterial and fungal populations were quantified using the serial dilution plate count technique on Nutrient Agar and Potato Dextrose Agar media, respectively. Data were analysed using paired t-tests, one-way ANOVA followed by Tukey's HSD test, Pearson's correlation analysis and Cohen's d effect size. Results: Healthy rhizosphere soils contained significantly higher bacterial and fungal populations than wilt-affected soils. Mean bacterial populations were 2.51 × 10⁶ and 2.09 × 10⁶ CFU g⁻¹ soil in healthy and wilt-affected fields, respectively, while fungal populations were 7.95 × 10⁴ and 6.73 × 10⁴ CFU g⁻¹ soil, respectively. Fungal populations were significantly higher in black Vertisol soils than in red Alfisol soils, whereas bacterial populations were not clearly separated by soil type. A significant negative bacterial–fungal correlation was observed only in wilt-affected soils (r = −0.28, P = 0.032), indicating disease-associated alteration in microbial balance. Conclusion: Fusarium wilt was associated with a significant decline in culturable rhizosphere microbial populations in pigeonpea. The findings provide baseline information on rhizosphere microbial dynamics across contrasting soil types and highlight the importance of conserving beneficial soil microorganisms for sustainable wilt management in pigeonpea production systems.