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Etiolated Maize Mesocotyls: A Tool for Investigating Disease Interactions. D. Heim, Graduate research assistant, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907; R. L. Nicholson(2), S. F. Pascholati(3), A. E. Hagerman(4), and W. Billett(5). (2)(3)(4)(5)Associate professor, graduate research assistant, post-doctoral associate, and technical assistant, respectively, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 73:424-428. Accepted for publication 26 August 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-424.

Etiolated mesocotyls of maize cultivars with differential resistance and susceptibility to Helminthosporium maydis race O and H. carbonum race 1, were useful for investigating host-parasite interactions. Mesocotyls and leaves were similarly susceptible or resistant to the pathogens. Pigmentation of the mesocotyl is an important indicator of its response to a pathogen. Uninoculated mesocotyls placed in the light accumulated anthocyanin pigments as a linear function of time. Anthocyanins also accumulated in resistant host-parasite combinations, and eventually their concentration equaled or exceeded that of uninoculated controls. A prominent zone of intense anthocyanin pigmentation often surrounded restricted lesions in resistant interactions. In susceptible host-parasite combinations, however, a significantly lower anthocyanin concentration was evident as early as 24 hr after inoculation and always prior to visible lesion development. In susceptible interactions, less anthocyanin accumulated than in uninoculated controls.

Additional keywords: Colletotrichum graminicola, Helminthosporium turcicum, phenolics, resistance, Zea mays.