Yellow Vein Mosaic Disease in Okra(Abelmoschus esculentus L.):An Overview on Causal Agent,Vector and Management

Okra(Abelmoschus esculentus L.)belongs to the Malvaceae family and is one of the most essential and popular vegetables globally.It is rich in proteins,carbohydrates,and vitamins.Abiotic and biotic factors threaten okra productivity.Okra yellow vein mosaic disease(OYVMD)is the most destructive disease of okra.The causal agent,[i.e.,Okra yellow vein mosaic virus(OYVMV)]of this disease belongs to the family Geminiviridae and genus Begomovirus.OYVMV is a monopartite with additional ssDNA molecule.This virus has two components DNA-A for protein coding and DNA-B for symptoms induction.Whitefly transmits OYVMV in persistent manner.Characteristic symptoms of OYVMV infected okra plants are chlorosis,dwarfing,and yellowing of veins and fruits.High temperatures with moderate rainfall enhance the development of OYVMV disease and the whitefly population.However,high humidity with low temperature and rainfall has no significant role in developing the OYVMD and whitefly population.Moreover,the virus also affects the secondary metabolites in the infected okra plants.The virus can be managed through various strategies including the application of plant defense activators,the development of resistant varieties and by controlling its vector via pesticides and plant extracts.Various plant defense activators such as monopotassium phosphate(KH2PO),salicylic acid,benzoic acid,and citric acid enhance resistance in okra against OYMVD.In addition,the resistance to OYMVD can also be achieved by successfully incorporating high yielding but resistant cultivars of acceptable quality.In this review,we have discussed history,economic impact,symptomology,disease development under a natural environment,genetics and management of OYVMV.

Overview of Strain Characterization in Relation to Serological and Molecular Detection of Citrus tristeza Closterovirus

Tristeza is a devastating viral disease in all the citrus growing countries throughout the world and has killed millions of citrus trees in severely affected orchards.The citrus species grafted on sour orange rootstock are affected by this disease.Predominantly,the sweet orange,grapefruit and lime trees grafted on sour orange exhibit severe symptoms like quick decline,vein clearing,pin holing,bark scaling and degeneration leading to variable symptoms.Symptomatic expression of Citrus tristeza virus(CTV)in different hosts has been attributed to virus isolates which are from severe to mild.Different serological and molecular assays have been deployed to differentiate the strains of CTV.Citrus tristeza virus is diversified towards its strains on the basis of biological,serological and molecular characterization.Phenotypic expression is due to genetic alteration and different molecular basis have now been adopted for strain differentiation.This review will give a brief idea about the different CTV isolates,their characterization based on nucleic acid and serological assays.Different methods along with salient features for strain characterization has also been reviewed.This review will also open the new aspects towards formulation of management strategies through different detection techniques.