ABSTRACT
The kingdom Protozoa contains the acellular (plasmodial), free-living, slime moulds that are colourful, non-parasitic organisms, move like amoebae that can resemble plant pathogens. Protozoa are at the base of the eukaryotic branch of the ‘tree of life’ and are believed to be the first eukaryotes to arise. •Phytomonas is believed to have arisen from a single monoxenous lineage of insect parasitizing trypanosomatids some 400 million years ago. They are followed by Phytomyxea, which are part of the Rhizaria supergroup and include agriculturally important plant pathogens, vectors of phytoviruses and species that infect marine plants and algae. Within the plant, the organisms can be in several flagellated stages: mostly promastigote with some paramastigotes in the phloem and lacticiferous tubes, and amastigote form in the latex.
