Chlorophyll Fluorescence Imaging for Detection of Bean Response to Pseudomonas syringae in Asymptomatic Leaf Areas

Abstract

The physiological condition of infected plants can be monitored prior to appearance of symptoms using non-destructive methods such as chlorophyll fluorescence imaging. A number of studies using different chlorophyll fluores- cence imaging prototypes have shown that photosynthesis is severely impaired in symptomatic and asymptomatic leaves of fungal- or virus-infected plants. However, little information is available for bacterial infected plants. In the present study, chlorophyll fluorescence imaging was used to analyse the response elicited in Phaseolus vulgaris after inoculation with Pseudomonas syringae pv. phaseolicola 1448A (compatible interaction) and P. syringae pv. tomato DC300 (incompat- ible interaction). Quenching analysis was carried out and images of the different chlorophyll fluorescence parameters were obtained on infected plants as well as in mock controls at different post-inoculation times. Of the different parameters ana- lysed, effective photosystem II quantum yield and non-photochemical quenching maximized the differences between plants infected with either of both pathogens. Significant changes in these parameters were observed before the appearance of visual symptoms. Images of effective photosystem II quantum yield did not reveal any differences between compatible and incompatible infected plants. In contrast, images of non-photochemical quenching showed considerable difference between such plants.