Inducing Resistance to <scp> <i>Xanthomonas citri</i> </scp> pv. <scp> <i>fuscans</i> </scp> in Bean ( <scp> <i>Phaseolus vulgaris</i> </scp> ) Cultivars Using Biocontrol Agents and Inducers

ABSTRACT Common bacterial blight (CBB), caused by Xanthomonas citri pv. fuscans (Xcf), is the predominant bacterial disease affecting beans, requiring effective control strategies. This study assessed the efficacy of biological agents and inducers in enhancing resistance against X. citri pv. fuscans while examining their impact on yield in bean cultivars IPR Campos Gerais and IPR Tangará. The biological agents Bacillus amyloliquefaciens and Trichoderma harzianum were assessed, alongside inducers citric acid, sulphur, methyl salicylate, potassium silicate and acibenzolar‐S‐methyl (ASM). Different application modes were tested: seed treatment (T1), seed treatment with foliar spray at stage V3 (T2), foliar spray only at V3 (T3) and seed treatment with foliar spray at stages V3 and R5 (T4). Disease severity, production of total soluble proteins (TP), peroxidase (POD), phenylalanine ammonia‐lyase (PAL) and total phenolic compounds (TPC), and various yield components were measured. All products reduced Xcf severity. In IPR Campos Gerais, T . harzianum , sulphur (T2 and T3), B. amyloliquefaciens and citric acid (T2) were more effective than ASM. In IPR Tangará, T . harzianum (T1, T3, T4), B. amyloliquefaciens , and citric acid (T3) outperformed ASM. Following Xcf inoculation, there was an increase in TP, POD and PAL activities. There was a general trend for B. amyloliquefaciens and sulphur to enhance POD activity, while citric acid and T . harzianum increased TPC activity. The 1000‐grain weight (TGW) and final yield were significantly impacted, especially in IPR Campos Gerais. The use of agents like B. amyloliquefaciens , T . harzianum , citric acid and sulphur provided effective protection against CBB, offering valuable insights for the sustainable management of this disease.