Citrus psorosis virus
Encyclopedia
Citrus psorosis virus is a plant
pathogenic virus
infecting citrus
plants worldwide. It is considered to be the most serious and detrimental virus pathogen of these trees.
, CEVd and Spiroplasma citri by testing with DTBIA, tissue print hybridization and Diene's stain respectively (Ghazal et al., 2008).
CPsV-EG isolate was transmitted from infected citrus to citrus by syringe and grafting and herbaceous plants by forefinger inoculation and syringe. The woody indicators and rootstocks were differed in response to CPsV-EG isolate which appeared as no-response, response, sensitivity and hypersensitivity. A partial fragment of RNA3 (coat protein gene) of CPsV-EG (-1140bp and -571bp) was amplified by reverse transcription-polymerase chain reaction (RT-PCR) from grapefruit tissues using two sets primers specific CPsV (CPV3 and CPV4) and (PS66 and PS65) respectively. The virus under study was identified as CPsV-EG isolate according to biological, serological and molecular characters. The serological characters represented as the antigenic determinants of CPsV-EG isolate related to monoclonal antibodies specific CPsV strain where as appeared precipitation reaction by DAS-ELISA and DTBIA (Ghazal et al., 2008).
CPsV-EG was detected on the basis of biological indexing by graft inoculation which gave oak leaf pattern (OLP) on Dweet tangor and serological assay by DAS-ELISA using Mab specific CPsV. CPsV-EG was reacted with variable responses on 16 host plants belonging to 6 families. Only 8 host plants are susceptible and showed visible external symptoms which appeared as local, systemic and local followed by systemic infections (Ghazal et al., 2008).
In general CPsV-EG-infection affects the upper epidermis
of the leaf which is composed of non-tabular parenchyma cells covered by a thin layer of cuticle
. Crystal idioblast (CI) containing cells are lacking in the palisade layer and protrude into the epidermis. The oil glands are lacking compared with healthy leaf. Secondary growth occurs in midvein and major lateral veins in smaller veinlets. The vein endings consist of a single trachoid strand of elongated parenchyma
cells enclosed by the bundle sheath compared with healthy ones (Sofy et al., 2007).
The ultrastructure of infected leaves showed a number of changes. Infected cells have large numbers of abnormal chloroplast
s, mitochondria and hypertrophied nuclei. Cells of CPsV-EG infected citrus plants have abnormally elongated and curved mitochondria. The nuclei have several dark stained bodies, which are displaced toward nucleus periphery along the nuclear envelope. Sometimes nucleolus
appear abnormally shaped. Inclusion bodies that may contain virus particles are also found (Sofy et al., 2007).
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
pathogenic virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
infecting citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
plants worldwide. It is considered to be the most serious and detrimental virus pathogen of these trees.
Isolation
The Citrus psorosis virus Egyptian strain (CPsV-EG) was isolated from naturally infected citrus grapefruit (Citrus paradisi Macf.) at ARC. The grapefruit used for CPsV-EG isolatation was found to be free from CTVCTV
-Television:* CTV Television Network, a private Canadian broadcast television network** CTV Two, a private Canadian broadcast television network** CTV News Channel , an all-news cable channel owned by CTV Television Network...
, CEVd and Spiroplasma citri by testing with DTBIA, tissue print hybridization and Diene's stain respectively (Ghazal et al., 2008).
CPsV-EG isolate was transmitted from infected citrus to citrus by syringe and grafting and herbaceous plants by forefinger inoculation and syringe. The woody indicators and rootstocks were differed in response to CPsV-EG isolate which appeared as no-response, response, sensitivity and hypersensitivity. A partial fragment of RNA3 (coat protein gene) of CPsV-EG (-1140bp and -571bp) was amplified by reverse transcription-polymerase chain reaction (RT-PCR) from grapefruit tissues using two sets primers specific CPsV (CPV3 and CPV4) and (PS66 and PS65) respectively. The virus under study was identified as CPsV-EG isolate according to biological, serological and molecular characters. The serological characters represented as the antigenic determinants of CPsV-EG isolate related to monoclonal antibodies specific CPsV strain where as appeared precipitation reaction by DAS-ELISA and DTBIA (Ghazal et al., 2008).
CPsV-EG was detected on the basis of biological indexing by graft inoculation which gave oak leaf pattern (OLP) on Dweet tangor and serological assay by DAS-ELISA using Mab specific CPsV. CPsV-EG was reacted with variable responses on 16 host plants belonging to 6 families. Only 8 host plants are susceptible and showed visible external symptoms which appeared as local, systemic and local followed by systemic infections (Ghazal et al., 2008).
Histology
Young grapefruit leaves of both healthy and CPsV-EG infected plants have been studied histologically and ultrastructurally (Sofy et al., 2007).In general CPsV-EG-infection affects the upper epidermis
Epidermis
Epidermis may refer to:* Epidermis , in plants, the outermost layer of cells covering the leaves and young parts of a plant* Epidermis , the outermost layer of the skin of a human...
of the leaf which is composed of non-tabular parenchyma cells covered by a thin layer of cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
. Crystal idioblast (CI) containing cells are lacking in the palisade layer and protrude into the epidermis. The oil glands are lacking compared with healthy leaf. Secondary growth occurs in midvein and major lateral veins in smaller veinlets. The vein endings consist of a single trachoid strand of elongated parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
cells enclosed by the bundle sheath compared with healthy ones (Sofy et al., 2007).
The ultrastructure of infected leaves showed a number of changes. Infected cells have large numbers of abnormal chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
s, mitochondria and hypertrophied nuclei. Cells of CPsV-EG infected citrus plants have abnormally elongated and curved mitochondria. The nuclei have several dark stained bodies, which are displaced toward nucleus periphery along the nuclear envelope. Sometimes nucleolus
Nucleolus
The nucleolus is a non-membrane bound structure composed of proteins and nucleic acids found within the nucleus. Ribosomal RNA is transcribed and assembled within the nucleolus...
appear abnormally shaped. Inclusion bodies that may contain virus particles are also found (Sofy et al., 2007).