Phytoplasma: A plant pathogen that cannot be ignored in agricultural production—Research progress and outlook

Abstract

Phytoplasmas are phloem‐restricted plant‐pathogenic bacteria transmitted by insects. They cause diseases in a wide range of host plants, resulting in significant economic and ecological losses worldwide. Research on phytoplasmas has a long history, with significant progress being made in the past 30 years. Notably, with the rapid development of phytoplasma research, scientists have identified the primary agents involved in phytoplasma transmission, established classification and detection systems for phytoplasmas, and 243 genomes have been sequenced and assembled completely or to draft quality. Multiple possible phytoplasma effectors have been investigated, elucidating the molecular mechanisms by which phytoplasmas manipulate their hosts. This review summarizes recent advances in phytoplasma research, including identification techniques, host range studies, whole‐ or draft‐genome sequencing, effector pathogenesis and disease control methods. Additionally, future research directions in the field of phytoplasma research are discussed.

Paulownia Witches’ Broom Disease: A Comprehensive Review

“…Phytoplasmas are wall-less bacterial plant pathogens provisionally classified to the 'Candidatus Phytoplasma' genus [1,2]; they are mainly transmitted by insect vectors and inhabit the phloem of plants and the hemolymphs of insects. After colonization, phytoplasmas secrete effector proteins into cytoplasm of the host plant cells.…”

“…These effectors interact with certain target proteins in the plant cell, manipulate several host metabolic pathways inducing a series of disease symptoms that includes witches' broom (shoot proliferation), phyllody (leafy flower) and virescence, leaf yellowing and decline, stunted and little leaf, white leaf, purple top and other malformations. Some of the symptoms, such as witches' broom and phyllody, increase the prevalence of short branches and small young leaves, enhancing attraction of insect vectors and thus benefit the spread of phytoplasmas [1,2].…”

Prevalence and genetic diversity of phytoplasmas infecting different crops in Egypt

“…Plant-pathogenic phytoplasmas lack cell walls and have a pleomorphic form, a diameter of 200-800 nm, and a very tiny genome of approximately 680 -1600 kb. They are Gram-positive Mollicutes that live in plant phloem tissues and insect hemolymph, particularly in leafhoppers and plant hoppers (Weintraub and Beanland, 2006;Bertaccini et al, 2014;Yang et al, 2020;Wang et al, 2022Wang et al, 2024. Phytoplasmas can cause a variety of symptoms, including shoot proliferation, stunting, phyllody, virescence, witches' broom, big bud, little leaf, giant calyx, floral malformation, and vascular discoloration (Bertaccini 2007;Omar et al, 2014;Kumari et al, 2019;Wang et al, 2022;Bertaccini, 2022;Kirdat et al, 2023 ).…”

“…Many factors influence the geographical distribution of phytoplasma strains, including human activity, insect vector feeding behavior (monophagous, oligophagous, or polyphagous), and phytoplasma host range (Hogenhout et al, 2008;EPPO, 2017). Phytoplasma diseases have been reported in various countries worldwide (Bertaccini and Duduk, 2010;Marcone et al, 2016;Kumari et al, 2019;Pierro et al, 2019;Hemmati et al, 2021;Wang et al, 2022;Xiaoyan et al, 2023;Wang et al, 2024). Phytoplasma diseases have previously been documented in Egypt on tomatoes (El-Banna et al, 2007;Omar and Foissac 2012;Ahmed et al, 2014), faba beans (Hamed et al, 2014;Ahmed et al, 2022b), and sesame (El-Banna et al, 2013;Youssef et al, 2018;and Ahmed et al, 2022a).…”