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Research

   The bacterial wilt pathogen, Ralstonia solanacearum, causes one of the most devastating bacterial diseases of plants worldwide, affecting hundreds of plant species including many major crops such as tomato and potato.  In developing countries, it is estimated that this economically important disease results in over one billion US dollars lost annually for the potato industry alone.  Because this pathogen is typically restricted to warm climates, the losses resulting from bacterial wilt are particularly acute for subsistence farmers living in equatorial zones within Africa and India. 


   The map below, created by the European Plant Protection Organization, shows the spread of the bacterial wilt pathogen, with red circles showing countries that are affected.  Spread of cold-tolerant strains and future increases in global temperature are likely to result in an expanded geographical range for Ralstonia

 Bacterial wilt map

  While the resistance mechanisms that protect plants against bacterial pathogens of leaves are well-studied, little is known about resistance to Ralstonia, which typically infects plants via the root systems and ultimately colonizes the plant vasculature resulting in wilting and death.

Diagram of plant root, bacteria in blue: 

Bacterial wilt entry 

 (root photo adapted from Swarup et al Nature Cell Biology 2005; Geranium photo from Wisconsin Department of Agriculture)

 During infection, bacteria inject proteins directly into the cytoplasm of the plant cell.  These proteins are called “effector proteins”.  

Effector injection 
  The Mitra lab studies the role of these effector proteins in plant pathogenesis and plant defense.  We are studying plant root responses to effectors of this bacterial pathogen with the goal of identifying effectors that are recognized, and those that lead to plant cell death.