<p>Bean (<i>Phaseolus vulgaris</i> L.) is one of the most intensively grown vegetables in the world due to their economic significance and high nutritional value. The multiple objectives of this study were (i) to isolate and identify <i>Pseudomonas syringae</i> pv. <i>phaseolicola</i> (Psp), <i>Xanthomonas axonopodis</i> pv. <i>phaseoli</i> (Xap) and <i>P. syringae</i> pv. <i>syringae</i> (Pss) on bean plants cultivated in different regions of Türkiye; (ii) to evaluate the resistance of bean genotypes to representative strains of Psp, Xap, and Pss; and (iii) to characterize the resistance mechanisms involved in the resistance of bean genotypes through biochemical, histochemical, and microscopic studies. Bacterial pathogens were identified by biochemical, Microbial Identification System (MIS), and serological (ELISA) tests. The results showed the prevalence of Psp, Xap, and Pss strains in bean plants cultivated in the Central Anatolia, Aegean, Marmara and Mediterranean regions of Türkiye. The disease reactions of bean genotypes to bacterial strains from different regions were determined. Accumulation of reactive oxygen species (H₂O₂) and secondary metabolites such as lignin, phenolics, callose, and phytoalexins, which are among the plant resistance mechanisms that play a key role in preventing pathogen development, were revealed by histochemical and biochemical analyses in bean genotypes during compatible and incompatible interactions. Cells of bean plants resistant or tolerant to the tested bacterial species activated defense mechanisms—such as phytoalexin synthesis and the accumulation of H₂O₂, lignin, callose, and phenolics in the cell walls—during incompatible interactions. A strong correlation was observed between resistance and these mechanisms, which were rapid and extensive in incompatible interactions compared to compatible interactions. Incorporating these results into breeding programs could accelerate the development of bean cultivars with durable resistance to bacterial blight disease agents.</p>