Summary Research Sporulation and Dissemination of Hypovirulent Strains of the Chestnut Blight Fungus at the University of Kentucky

ABSTRACT.--Old chestnut blight cankers support abundant sporulation of both Ceratocystis microspora and C. eucastaneae, and were more attractive to insects than younger cankers where Ceratocystis is absent. Additional research indicates that Ceratocystis-laden chestnut bark can function in attracting insects to non-chestnut substrates. Ceratocystis perithecia were observed two months after their inoculation into established virulent (V) or hypo-virulent (H) cankers. These results suggest that introduction of Ceratocystis species into H cankers may enhance insect dissemination of sparsely sporulating H strains. In vitro studies suggest that establishment of Ceratocystis in blight cankers is enhanced by the action of Endothia parasitica to modify inhibitory compounds in healthy bark and to produce metabolites which directly stimulate Ceratocystis. Both C. eucastaneae and, to a lesser degree, C.microspora inhibited growth and sporulation of E. parasitica on artificial media. Host range studies with excised dormant stems show that, of 23 species tested, development of selected V and H strains was supported by Acer rubrum, A. pennsylvanicum, Quercus velutina, Q. rubra, Betula lutea, and Castanea dentata. Dissemination of auxotrophic H strains has not been observed in study plots after 2 growing seasons.

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Author(s): John S. Russin, Louis Shain, G. L. Nordin

Publication: American Chestnut Proceedings - 1982