Projects on Systemic Induced Resistance

The most desirable form of resistance is systemic.  Systemic induced resistance (SIR) is also usually broad spectrum (effective against many pathogens).  Unfortunately, although SIR has been developed for several model plants, it has not been developed in many crop plants, including soybean.

Farmers recently noticed that the herbicide lactofen protects soybean plants in the field against some soybean pathogens.  We have extensively studied the effects of lactofen on soybeans (pdf file) and demonstrated that it may induce truly systemic protection against several classes of pathogens.  We are currently working out the variables affecting the response to optimize its use in the field.

Shown to the left is systemic protection of soybean leaves against a bacterial pathogen, Pseudomonas syringae pv. glycinea.  Lower leaves were treated with lactofen, and eight days later upper leaves (shown in picture) were inoculated with the pathogen.  As seen, lactofen caused the disease to be contained in a necrotic lesion in the  inoculated upper leaves (Larue and Graham, unpublished).  We are currently studying both secondary product metabolism and defense gene expression in both the lactofen-treated and protected leaves.