Rhizosphere microbiome and calcium synergy drive suppression of Ceratocystis paradoxa in tropical coconut soils

Ceratocystis paradoxa is a polyphagous, soil-borne pathogen that threatens various crops worldwide. This study evaluated soil suppressiveness against C. paradoxa and identified key biotic and abiotic factors involved. Suppressiveness was assessed using banana peel baits, followed by comparative analysis of microbial communities and soil physicochemical properties in five suppressive and five conducive soils. Suppressive soils exhibited higher culturable bacterial populations and enrichment of Actinobacteria, Proteobacteria, Firmicutes, and Acidobacteria, particularly Solirubrobacter, Actinoplanes, and Conexibacter. Favorable physicochemical traits included higher pH, calcium content, cation exchange capacity, base saturation, and sand content. Calcium carbonate amendments enhanced suppressiveness, particularly at pH 7.0. Transferring the microbiota from suppressive soils to conducive subsoils, combined with calcium carbonate, also induced suppressiveness. These results highlight the synergistic role of microbial communities and soil chemistry, particularly pH and calcium in pathogen suppression. Calcium promoted microbial activity and stabilized pH, contributing to reduced disease incidence. This integrated strategy offers a promising avenue for sustainable management of C. paradoxa in tropical agriculture through microbiome manipulation and soil amendments.