Chestnut bark tannin assays and growth of chestnut blight fungus on extracted tannin

Tannins extracted from the green bark of each of two Chinese, Japanese, and American chestnut trees were assayed in a protein-binding test. Four levels of tannins were added to a buffered, minimal growth medium, and a standard, virulent strain of the chestnut blight fungus was grown. There were only slight differences in protein binding between the extracts from different species. Fungal growth was better with tannin than without, but there was no difference between species extracts in their ability to improve fungal growth rate. There was also no inhibition of blight fungus growth by any of the tree tannins, so tannin toxicity is not the reason for Asian chestnut tree resistance.