Fungi fight fungi

​Nearly all living forms of life develop means of fighting off potential pathogens.  Corn cells produce specific enzymes to restrict and inhibit growth of most microorganisms.  Resistance to the very few that may be able to overcome most of inhibitors is usually a general compound, its effectiveness often related to amount of the inhibitor and the timing of its production.  The latter often is related to turning on its production based upon detection of the invader.
 
Most fungal species are dependent upon receiving nutrition from dead plant and animal sources partly because the anti-microbe inhibitors are not present.  However, there are many competitors for the same source of nutrition.  Consequently, natural selection favored production of metabolites that ward off competitors.  This is apparent to those of us that culture bacteria or fungi in petri dishes and observe contaminants warded off by another species of bacteria or fungus.  
 
This observation in 1928 led to the initial penicillin, as the fungal species of Penicillium warded off bacteria contaminating a petri dish.  Many other antibiotics were and continue to be isolated from fungi.
 
The mushroom Strobilurus tenacellus is a fungus that spends most of its life feeding on decaying pine cones in soils of European and Asian forests.  Like many mushroom species most of the fungus is not seen until it forms the reproductive mushroom structure above ground.  Beneath the surface, however, it fights off competitors by producing a compound called strobilurin.  This compound is apparently effective against many bacterial and fungal species.  It inhibits the energy production in mitochondria and gains an advantage for this fungal species by having genes blocking the strobilurin from attaching to its own cells.  Several other wood-rotting fungi also produce similar compounds to serve the same function of fighting competitors.
 
Obviously, the activity of these compounds makes them attractive as potential fungicides for crops such as corn.  Companies have modified the compounds to make them more stable when exposed to light and allow them to attach to leaves for enough time to be effective.  Many current corn fungicides use forms of strobilurin derived from cultures of these fungi.  
 
Adequate and economic restriction of potential damage to corn grain production requires a balance of resistance systems in the corn plant and adding metabolites from fungi.