Life History Studies of Mycosphaerella tassiana and M. typhae

Abstract

Mycosphaerella tassiana (de Not.) Johans. was grown in agar culture and produced mature ascostromata. A period of cold (5[degree]C), not less than 6 weeks, was necessary before maturation could be completed. The vegetative condition included a conidial stage identified as Cladosporium herbarum Link ex Fries. Ascostromata were formed from cells of the hyphae which enlarged and divided many times. Within the locule of the stroma certain cells became multi-nucleate. Neither trichogynes nor spermatia were found and the origin of the ascogenous cells could not be determined. Asci developed from the ascogenous cells and produced 8 uniseptate spores, each cell multinucleate. The chromosome number was determined as n = 4. Mycosphaerella typhae (Lasch) Lindau developed in a similar manner to M. tassiana. The species differs in not producing a conidial stage, in its smaller size, and in more southern distribution. The chromosome number of M. typhae is not known. Both species belong in the subgenus Didymellina of Mycosphaerella. The Ascostromata, both in nature and in culture, may be single, grouped, or aggregated to form a stroma containing numerous locules. These species, as well as others, indicate that the genus should be considered a member of the family Dothideaceae, rather than separated into the family Mycosphaerellaceae.