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SUMMARY
Gonatorhodiella highlei A. L. Smith is found in nature as a biotrophic parasite of Nectria coccinea (Pers.) Fries on bark of American beech (Fagus grandifolia Ehrh.). The host range was extended to include Verticillium albo-atrum Reinke & Barthold, Cladosporium sp., Tritirachium sp., Graphium sp., and Chaetomella raphigera Swift. The source and concentration of nitrogen in the medium Effected the growth of the parasite on N. coccinea. Certain organic nitrogen sources at high concentrations (above 0.42 g nitrogen/liter) were inhibitory, due to liberation of ammonia by the host. The concentration of thiamine in the medium also affected growth of the parasite on N. coccinea. Parasitism occurred only when the concentration of thiamine was higher than the optimum for host growth.
White light (200 ft-c) inhibited growth of G. highlei on Nectria coccinea and Tritirachium sp. and inhibited axenic growth of the parasite. The effect was directly on the parasite and was not due to light-induced changes in the medium. A nutrient required G. highlei for spore germination was found in beech bark. The compound is water soluble, organic, and has a low molecular weight. Both this compound and mycotrophein, an unidentified growth factor, are required for axenic growth.