The Characterization of Septoria lycopersici Pathogenicity in Micro Tom Tomatoes

Septoria lycopersici is a foliar fungal pathogen of tomatoes. This pathosystem has been well characterized with respect to the tomato antimicrobial secondary metabolite, alpha‐tomatine and the fungal detoxifying enzyme, tomatinase. However, there are many gaps in our knowledge of other aspects of the S. lycopersici pathogenicity. We know that fungal spores germinate on tomato leaves and grow biotrophically. The hyphae then invade the leaf apoplast via open stomata or wounds. At some point, S. lycopersici begins to damage the surrounding plant tissue. One of the aims of this project is to characterize the process of fungal infection with light, confocal fluorescence and scanning electron microscopy. This will provide the basis for further investigations of the key virulence factors present in S. lycopersici as well as potential defense mechanisms. We will also be assessing the ability of S. lycopersici to infect the dwarf tomato cultivar, Micro Tom. If Micro Tom tomatoes are susceptible, they could become the preferred host cultivar, due to their rapid life cycle. If Micro Tom tomatoes are not susceptible, this provides a source for possible resistance genes. In addition, the closely related wheat fungal pathogen, Mycosphaerella graminicola has been reported to be dimorphic with only the filamentous form able to infect plant hosts. The switch from yeast‐like to filamentous growth is regulated by a mitogen‐activated protein kinase. There are also reports that the switch to filamentous growth can be controlled by temperature. We will be characterizing the growth phase of S. lycopersici at various temperatures to determine if this fungal pathogen is also dimorphic. Support or Funding Information Lawrence Technological University Department of Natural Sciences