The first step in identifying a potential resistance gene is to examine ways in which other organisms combat fungal attacks. One defense mechanism to combat fungi directly is with enzymes designed to break down their cell walls. Many plant species, including chestnut, use this defense mechanism. Another defense mechanism is for an organism to release very short strands of specialized defense proteins just long enough to span the cell membranes of attacking fungi. Dozens of these small proteins clump together, forming small holes in the membrane.
Essential minerals leak out and the fungus dies.
Although not as direct an attack as an enzyme that simply rips apart the fungal cell wall, these tiny proteins can be just as effective. A number of different organisms including some moths, frogs, bees, pigs, and probably many others, produce mini proteins with these properties but to our knowledge, American chestnut does not yet. Dr. Powell and his graduate students are testing several of these small proteins and plan to test more to see which are most effective against the blight pathogen. The ideal mini protein would be one that is deadly to the fungus at a very low concentration, but causes the plant no harm even at a much higher concentration. In addition, it should be completely non-toxic to humans or wildlife who will someday eat the chestnuts.