From Defense to Resilience: Exploring the Metabolic and Biochemical Responses of Beans to Halo and Common Blight Pathogens

In the context of bean production, the insidious presence of Pseudomonas savastanoi pv. phaseolicola (Psp) and Xanthomonas axonopodis pv. phaseoli (Xap) is a formidable challenge, exerting significant negative impacts in Türkiye. This study aimed to estimate the chlorophyll carotenoid contents and phenolic compounds to determine the effects of pathogen damage on bean pigment contents. Physiological and biochemical changes were observed after bacterial pathogens attacked susceptible and resistant bean plants. Chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents were measured using a spectrophotometer 72 h after pathogen inoculation, and phenolic compounds were measured by high-performance liquid chromatography (HPLC) at 12 and 72 h after Xap and Psp inoculation in susceptible and resistant bean plants. Although the contents of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in the leaves of cultivar Aras-98 decreased after both pathogen treatments, there was no change in the leaves of the 36K genotype. HPLC revealed the presence of various amounts of phenolic compounds, namely, gallic, catechin, chlorogenic, caffeic, syringic, p-coumaric, rutin, q-coumaric, myricetin, and quercetin. In this study, the intricate ways in which pathogens influence metabolic processes within bean leaf tissue were investigated, with a focus on the resilient 36K and susceptible Aras98 genotypes. The insights obtained from our research are useful not only for our understanding of plant‒pathogen interactions but also as a foundational cornerstone for future endeavors in molecular pathological breeding. These findings provide guidance, illuminating pathways for the cultivation of robust, disease-resistant bean varieties.