In vitro culture response of common bean explants to filtrate from Pseudomonas syringae pv. phaseolicola and correlation with disease resistance

The in vitro culture responses from different explants of a race-specific resistant cultivar (Red Mexican) and a race-susceptible cultivar (Palmena) to halo-blight pathogen (Pseudomonas syringae pv. phaseolicola) were studied. Two kinds of filtrate obtained from a phaseolotoxin producer wild type and a non-producer mutant of P. syringae pv. phaseolicola race-7 were used. Callus formation of Red Mexican was significantly reduced in the presence of phaseolotoxin. Bud-shoot growth was more sensitive than callus formation to other metabolites present in the pathogen filtrate, but the presence of phaseolotoxin in the media showed a positive correlation between resistance to halo blight race-7 pathogen and bud-shoot growth. Our results indicate that differential in vitro responses are influenced by the plant genotype and by the metabolite composition and concentration of the filtrate.