Characterization of Botrytis–plant interactions using PathTrack^©—an automated system for dynamic analysis of disease development

Abstract

The measurement of disease development is integral in studies on plant-microbe interactions. To address the need for a dynamic and quantitative disease evaluation, we developed PathTrack , and used it to analyse the interaction of plants with Botrytis cinerea. PathTrack is composed of an infection chamber, a photography unit and software that produces video files and numerical values of disease progression. We identified a previously unrecognized infection stage and determined numerical parameters of pathogenic development. Using these parameters, we identified differences in disease dynamics between seemingly similar B. cinerea pathogenicity mutants, and revealed new details on plant susceptibility to the fungus. We showed that the difference between the lesion expansion rate on leaves and colony spreading rate on artificial medium reflects the levels of the plant immune system, suggesting that this parameter can be used to quantify plant defence. Our results shed new light and reveal new details of the interaction between the model necrotrophic pathogen B. cinerea and plants. The concept that we present is universal and may be applied to facilitate the study of various types of plant-pathogen association.

BcXYG1, a Secreted Xyloglucanase from Botrytis cinerea, Triggers Both Cell Death and Plant Immune Responses

“…To gain insight into possible unnoticed effects caused by BcXYG1, particularly during the early infection stage, we characterized infection of the bcxyg1 overexpression and deletion strains using the PathTrack system. This system allows for sensitive and quantitative analysis of infection dynamics and, therefore, can reveal small changes in disease development (Eizner et al, 2017). The pathogenic behavior of the Dbcxyg1 deletion strain was similar to that of the wild type in all of the examined parameters, including time and magnitude of early necrosis, break time, and lesion expansion rate (Fig.…”

“…Accordingly, mutants in NIP-encoding genes are expected to be affected specifically in the production of early necrosis, but not at the stage of spreading lesion. To determine the possible effect of BcXYG1 in an early stage of the disease, we analyzed the infection of bean leaves using PathTrack, a noninvasive, automated system for live imaging and quantitative measurement of disease development (Eizner et al, 2017). This analysis revealed that the leaves infected with the BcXYG1 overexpression strains OEXYG1 or OEMXYG1 produced earlier and more intense local necrosis.…”

“…BcXYG1 contributes to the establishment of the infection in early stages of pathogenic development. Bean leaves were inoculated with spores of the different strains, the leaves were photographed every 10 min, and the data were analyzed using PathTrack (Eizner et al, 2017). Images show selected time points during pathogenic development.…”

“…The primary leaves of 9-d-old bean were inoculated with 7.5-mL conidial suspensions (2 3 10 5 conidia mL 21 ), the infected plants were incubated in a humid chamber at 22°C under fluorescent illumination for 72 h, and the lesion diameter was then measured. When specified, PathTrack (Eizner et al, 2017) was used to determine infection kinetics and parameters.…”

“…The B. cinerea infection process includes two typical stages: an early stage characterized by local lesions followed by a late stage of fast-spreading lesions (Williamson et al, 2007). Recent studies of disease dynamics conducted with the aid of the PathTrack system led to the discovery of a third, intermediate stage, between the transition from local infection to lesion spreading (Eizner et al, 2017). Further analysis using this system revealed that differences in disease progression between the wild type and pathogenicity mutants were largely in parameters of the intermediate stage, highlighting it as the phase during which the fungus is most significantly exposed and affected by the plant defense.…”