In-Plate Quantitative Characterization of Arabidopsis thaliana Susceptibility to the Fungal Vascular Pathogen Fusarium oxysporum

Fusarium oxysporum, the causal agent of Fusarium wilt, is a hemibiotrophic root vascular
pathogen that infects more than 100 crop species. Like those from many root vascular pathogens, F. oxysporum infections remain asymptomatic in aerial organs until the fungus reaches the plant vasculature, where it then proliferates within xylem cells, preventing the transport of water and nutrients and eventually causing wilting and death of the infected plant. Studying the progression of root vascular pathogens in plants poses a unique set of challenges not observed in the study of other pathologies, mainly because primary infection takes place below ground and is not easily observable by eye. Currently, in vivo infection assays in which disease progression is characterized through the quantification of leaf wilting and plant death are used to assess plant susceptibility to root vascular pathogens. These techniques are slow to complete and can deliver variable results as they rely on a de visu classification of plant disease phenotypes. More importantly, spatial and temporal analyses of
disease progression in the root vasculature are difficult to obtain by these methods due to soil obstruction or lack of appropriate fluorescent fungal strain(s).

Apolonio I. Huerta, from the Sánchez-Rodríguez group (IMPB), has lead the development of a method to quantify F. oxysporum disease progression using the model plant Arabidopsis thaliana which relies on the analysis of in vivo root growth inhibition and root vasculature colonization. They employed a simple but effective in-plate infection assay using a host compatible, fluorescently labeled F. oxysporum strain to quantify vascular penetrations throughout the infection cycle. In parallel, they developed a strategy to determine root growth inhibition via the use of scanning bed images and a semi-automated computational image analysis pipeline. Using this method, they could reliably elucidate disease progression and possible disease resistance by looking at changes in the susceptibility of A. thaliana mutants to F. oxysporum (Kesten et al., 2019). The hope of the Sánchez-Rodríguez group is that the ease and effectiveness of their method allows for easy adaptation and use with other plant and root vascular pathogen interactions.

Link to the publication in external page "Current Protocols in Plant Biology".