Systemic Phytobiochemical Analysis of Elaeis guineensis Source–Sink Defence Networks Under Ganoderma spp. Colonization

ABSTRACT

Early diagnosis of basal stem rot (BSR) of Elaeis guineensis , caused by Ganoderma boninense , is restricted by limited understanding of presymptomatic host defence mechanisms and their underlying rhizospheric drivers. This study established an in situ spatial tri‐gradient framework (i.e., healthy→near affected→fully affected) across major production zones in southern Thailand to quantify macromorphological regressions alongside concurrent foliar and root biochemical signalling. Soil cores were systematically extracted across depth‐stratified grids to bridge the analytical gap between host physiological stress and subterranean environmental constraints. Our findings reveal that presymptomatic “near affected” palms act as a critical biological bridge, initiating a coordinated metabolic reorganization, marked by intermediate pigment loss (~38% chlorophyll b depletion) and localized antioxidant upregulation before visible canopy or structural decay. Under advanced colonization, total foliar chlorophyll dropped by up to 70.1%, accompanied by a 374.0% increase in root lipid peroxidation and a severe 62.9% depletion of root structural flavonoids. Factorial ANOVA and multivariate principal component analysis confirmed that these multi‐organ defence responses are significantly modulated by depth‐stratified edaphic matrices, with lower soil bulk density (0.94 ± 0.06 g/cm ³ ) and depleted organic carbon stocks (52.00 ± 3.28 t/ha) strongly correlating with accelerated pathogenesis. The novelty of this research lies in the simultaneous mapping of source–sink metabolic networks with high‐resolution subsurface soil properties, establishing the first spatially explicit diagnostic model for early BSR detection. This integrated bio‐edaphic approach provides a framework for conventional plantation management by linking early subclinical biomarkers with depth‐specific rhizosphere targets to enable site‐specific disease suppression in climate‐vulnerable agroecosystems.