Peronosporomycetes

Peronosporomycetes, also known as Oomycetes, are a phylum of fungus-like organisms within the kingdom Chromista. They can be found in aquatic, amphibious, or terrestrial environments, acting as saprotrophs (feeding on decaying matter) or parasites of higher plants.1

Unlike true fungi, Oomycetes lack chitin in their cell walls and have a predominantly diploid life cycle. They reproduce asexually through motile cells called zoospores, which possess flagella for movement. Sexual reproduction also occurs, resulting in non-mobile spores called oospores.12

Notable genera include Phytophthora, responsible for the Irish potato famine, and Plasmopara, which causes downy mildews. Water molds, such as Saprolegnia, are also part of this group. The order Peronosporales includes parasitic organisms with biflagellate zoospores.123