Induction of apoplast phenolics in pepper (Capsicum annuum) leaves in response to pathogenic bacteria

The objective of this study was to corroborate, in pepper, the response of tobacco to induce apoplast phenolics upon bacterial inoculation. Leaves of Bell peppers (Capsicum annuum), 6–8 weeks old, were inoculated with bacteria and analyzed for apoplast phenolics after different periods of incubation. Pseudomonas syringae pv. tabacci, 108 cfu ml−1, induced numerous phenolics to accumulate in the leaf apoplast after 24h. UPLC-UV chromatograms revealed about 15 UV-peaks, some containing several components. Using this bacterial isolate, it was found that all the fully developed leaves on a single plant had a similar phenolic response based on magnitude and composition of the phenolics. Between plants, the phenolic composition was also similar, although there was more variability. The magnitude of response was proportional to the bacterial concentration between 105-108 cfu ml−1. Plants inoculated with water or P. fluorescens, a saprophyte, had a negligible response. When pepper plants were inoculated with different bacterial pathogens, P. s. pv. tomato and pv. syringae, there were differences in the magnitude and composition of the phenolics after 24 h. A time course showed that phenolic accumulation was underway by 7 h and appeared to peak by 24 h. The bacterial induction of apoplast phenolics in pepper, described here, corroborates the similar response previously described for tobacco. The preliminary characterization by UPLC-UV/MS suggests the apoplast pheno...
Source: Physiological and Molecular Plant Pathology - Category: Molecular Biology Source Type: research