Section 8
Chapter 7,175

Cytogenetic study of heterothallic and homothallic isolates of peronospora parasitica

Sherriff, C.; Lucas, J.A.

Mycological Research 92(3): 302-310


ISSN/ISBN: 0953-7562
DOI: 10.1016/s0953-7562(89)80070-x
Accession: 007174779

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A cytogenetic study of heterothallic and homothallic isolates of the downy mildew fungus, Peronospora parasitica, is described. Stages of oospore formation and meiosis are illustrated and compared with earlier descriptions for P. parasitica and Bremia lactucae. At metaphase I of meiosis, a ring of four chromosomes was found in all isolates. By comparison with similar observations in other Oomycete fungi, this ring is interpreted as a reciprocal translocation complex between chromosomes carrying the mating-type alleles. In homothallic isolates a fifth chromosome was associated with the ring of four. The self-fertility of these isoaltes may therefore be due to the presence of a third mating-type allele on the fifth chromosome, a condition known as secondary homothallism.

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