Etiolated Maize Mesocotyls: A Tool for Investigating Disease Interactions

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Abstract
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 h after inoculation and always prior to visible lesion development. In susceptible interactions, less anthocyanin accumulated than in uninoculated controls.