The American chestnut (Castanea dentata) was once the dominant canopy tree along the eastern region of the United States. Cryphonectria parasitica, the causative agent of chestnut blight, was introduced from Asia in the early 1900's, and obliterated the chestnut population within 50 years. We sought to identify environmental microbes capable of producing factors that were fungicidal or inhibited growth of C. parasitica in the hopes developing a biological control of chestnut blight. We isolated a filamentous fungus that significantly inhibited the growth of C. parasitica upon co-cultivation. Extracellular fractions of this fungal isolate prevented C. parasitica growth, indicating that a potential fungicide was produced by the novel isolate. Sequence analysis of 18S rRNA identified this inhibitory fungus as Penicillium chrysogenum. Furthermore, these extracellular fractions were tested as treatments for blight in vivo using chestnut saplings. Scarred saplings that were treated with the P. chrysogenum extracellular fractions healed subjectively better than those without treatment when inoculated with C. parasitica. These data suggest that material secreted by P. chrysogenum could be used as a treatment for the American chestnut blight. This work may assist the reclamation of the American chestnut in association with breeding programs and blight attenuation. Specifically, treatment of small groves under the right conditions may allow them to remain blight free. Future work will explore the mechanism of action and specific target of the extracellular fraction.
Keywords: American Chestnut; Biological Control; Chestnut Blight; Inhibition; Penicillium.