Climate change and the potential global distribution of Agrobacterium tumefaciens: a MaxEnt modeling approach for...

Climate change is fundamentally altering the geographic ranges of plant-pathogenic microorganisms, with profound implications for global food security and agricultural sustainability. Agrobacterium tumefaciens, the gram-negative soil bacterium responsible for crown gall disease in over 140 genera of dicotyledonous plants, is among the most economically significant phytopathogens worldwide, yet its macroecological distribution under current and projected future climates has never been rigorously characterised. Here, we apply the Maximum Entropy algorithm (MaxEnt) to 415 quality-filtered georeferenced occurrence records - derived from the Global Biodiversity Information Facility (GBIF) - combined with five non-collinear WorldClim 2.1 bioclimatic variables selected through Pearson correlation analysis in JMP Pro 16, to model the current potential global distribution of A. tumefaciens and project its future habitat suitability for 2050 and 2070 under RCP 2.6 and RCP 8.5 emission scenarios using the BCC-CSM1-1 general circulation model. The model demonstrated excellent predictive performance (mean AUC = 0.959; TSS = 0.77). Under current climate, high and very high suitability was concentrated in western and central Europe, the eastern United States, northern India, and eastern China. Jackknife analysis identified mean annual temperature (BIO1) as the dominant climatic driver, followed by precipitation of the driest month (BIO14), precipitation seasonality (BIO15), isothermality (BIO3), and mean diurnal temperature range (BIO2). Future projections consistently indicated a poleward displacement of suitable habitat, with net gains at higher latitudes and progressive contraction of very high suitability zones in current core regions, effects that intensify markedly under the high-emission RCP 8.5 scenario by 2070. Limiting factor analysis in DIVA-GIS revealed that thermal insufficiency constrains distribution at high latitudes while precipitation seasonality and dry-season moisture deficits dominate in tropical and arid zones. These findings provide a spatially explicit and climatically informed evidence base for anticipating future shifts in crown gall disease risk and informing climate-adaptive phytosanitary management strategies.