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Mycosphaerella zeae-maydis sp. n., the Sexual Stage of Phyllosticta maydis. D. M. Mukunya, Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; C. W. Boothroyd, Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 63:529-532. Accepted for publication 1 November 1972. DOI: 10.1094/Phyto-63-529.

Mycosphaerella zeae-maydis sp. n. is described as the sexual stage of Phyllosticta maydis. Pseudothecia were observed in naturally infected corn leaf debris, and the fungus was readily cultured from overwintered plant material and from leaves infected during the growing season. Pseudothecia with mature ascospores form in culture at 21 C in darkness. The pseudothecia are about 140 µ in diam, the asci 45 to 65 × 9.6 to 12 µ, and the ascospores 15 to 20 × 5 to 6 µ. The ascospores are hyaline and two-celled, with the apical cell broader and longer than the lower cell and with a marked constriction at the septum. Cultures from single conidia and from single ascospores form pycnidia and conidia at 24 C in the light and produce symptoms characteristic of yellow leaf blight when used in the inoculation of corn. Characters differentiating the new species from M. zeae (= M. zeicola) and M. maydis are noted.