Abstract
The presence of phytoplasmas and their associated diseases is an emerging threat to vegetable production which leads to severe yield losses worldwide. Phytoplasmas are phloem-limited pleomorphic bacteria lacking the cell wall, mainly transmitted through leafhoppers but also by plant propagation materials and seeds. Phytoplasma diseases of vegetable crops are characterized by symptoms such as little leaves, phyllody, flower virescence, big buds, and witches’ brooms. Phytoplasmas enclosed in at least sixteen different ribosomal groups infecting vegetable crops have been reported thus far across the world. The aster yellows phytoplasma group (16SrI) is presently the prevalent, followed by the peanut witches’ broom (16SrII). Wide and overlapping crop and non-crop host ranges of phytoplasmas, polyphagous insect vectors, limited availability of resistance sources and unavailability of environmentally safe chemical control measures lead to an arduous effort in the management of these diseases. The most feasible control of vegetable phytoplasma diseases is a consequence of the development and implementation of integrated disease management programs. The availability of molecular tools for phytoplasma identification at the strain level greatly facilitated this kind of approach. It is moreover essential to understand the molecular basis of phytoplasma-vector interaction, epidemiology and other factors involved in disease development in order to reduce the disease outbreaks. Information on the knowledge about the most widespread phytoplasma diseases in vegetable crops is reviewed here in a comprehensive manner.
Highlights
Vegetables are short-duration crops, grown during different seasons of the year, which fetch high economic returns
The objective of this review is to provide a summary of the global status of phytoplasmas infecting vegetable crops
In the phylogeny based on 16S rDNA nucleotide sequences, phytoplasma ribosomal groups infecting vegetable crops are mainly enclosed into two major clades: the first consists of 4 ribosomal groups (16SrI, 16SrXII, 16SrXIII, and 16SrXVIII) and the second comprises 6 ribosomal groups (16SrII, 16SrIII, 16SrVI, 16SrVII, 16SrIX, and 16SrXXXI) (Figure 2)
Summary
Shweta Kumari1*, Krishnan Nagendran, Awadhesh Bahadur Rai, Bijendra Singh, Govind Pratap Rao and Assunta Bertaccini. Edited by: Giorgio Gambino, Institute for Sustainable Plant Protection, Italian National Research Council (IPSP-CNR), Italy. Reviewed by: Kenro Oshima, Hosei University, Japan Tim Dumonceaux, Agriculture and Agri-Food Canada (AAFC), Canada
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