Candidatus Phytoplasma trifolii

Authors: Zhao, Yan; Wei, Wei

Submitted to: Center for Agriculture and Biosciences International (CABI) Invasive Species Compendium
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2020
Publication Date: 7/1/2020
Citation: Zhao, Y., Wei, W. 2020. Candidatus Phytoplasma trifolii. Center for Agriculture and Biosciences International (CABI) Invasive Species Compendium. https://doi.org/10.1079/ISC.40854.20210200691.
DOI: https://doi.org/10.1079/ISC.40854.20210200691

Interpretive Summary: 'Candidatus Phytoplasma trifolii' is a small plant-pathogenic bacterium that parasitizes nutrient-conducting vessels of host plants. The bacterium has a broad range of hosts and a wide distribution around the globe. Susceptible plants include agriculturally important leguminous, solanaceous, and brassicas crops and environmentally important ornamentals and forest trees. 'Ca. Phytoplasma trifolii' infection can affect all stages of plant development, from vegetative growth to floral transition and fruit setting, resulting in significant commodity yield losses and quality reductions. This chapter details the biology, ecology, and geographic distributions of the bacterium, the plant diseases the bacterium induces, the insect vectors that spread the bacterium, and the good agricultural practices that may help preventing and managing the plant diseases. This chapter will be of interest to research scientists who study bacteria genetic diversity and to extension personnel who are concerned with phytoplasmal disease management. This information is also important to regulatory agencies for enhancing border control to prevent further spread of the phytoplasma.

Technical Abstract: he reference strain of 'Candidatus Phytoplasma trifolii' is the causative agent of clover proliferation (CP) disease of alsike clover (Trifolium hybridum). The disease was first reported in Canada in early 1960s. Initially, the etiological agent of the CP disease was mistakenly presumed to be a yellows-type virus. Subsequent investigations revealed that the disease was associated with infection by a mycoplasma-like organism, now termed phytoplasma. In the ensuing decades, 'Candidatus Phytoplasma trifolii' and genetically closely-related strains, collectively known as group 16SrVI or CP phytoplasmas, were found in the United States, Mexico, and many countries in Europe, Asia, and Oceana. These phytoplasmas are responsible for numerous diseases in diverse plant species, including agriculturally important leguminous, solanaceous, and brassicas crops, as well as environmentally important ornamentals and forest trees. 'Ca. Phytoplasma trifolii' resides in phloem sieve elements and are transmitted by phloem-feeding insects, mainly aster leafhopper (Macrosteles fascifrons) and beet leafhopper (Circulifer tenellus) in nature. While 'Ca. Phytoplasma trifolii' is not seed-borne, it can be spread through propagules such as cuttings, runners, bulbs, and tubers. This chapter details the biology, ecology, and geographic distribution of the group 16SrVI phytoplasmas, the plant diseases and symptoms the phytoplasmas induce, and the good agricultural practices that may help preventing and managing the plant diseases.