No abstract

The genus Citrus belongs to the Rutaceae or Rue family, sub-family Aurantoideae. The 5 commercially important fruit crops (sweet orange (C.sinensis .L.) tangerine (C. reticulata B.), grapefruit (C. paradisi M.), lemon (C.Limon. F) and lime (C. aurantifolia L.) are recognized as single species within Citrus. They are mainly cultivated in the subtropical and tropical regions of the world between 400 north and south latitude in over 137 countries on six continents (Ismail and Zhang, 2004). Plant viruses are highly prevalent and serious threat to cultivated plants and agricultural production in plants like vegetables and fruits worldwide. Viruses have evolved as combinations of genes whose products interact with cellular components to produce progeny throughout the plants and in most cases, to interact with a vector to be moved to other plants. These processes require several layers of precise interactions with the host. In general, the more conserved genes tend to be those whose products interact within the cell to replicate the viral genome (Fanny et a l., 2015). This process appears to be somewhat generic because many viruses have been found to be capable of multiplying in individual cells (protoplasts) but cannot move throughout the intact plant. The less conserved genes tend to be those that have evolved for interactions with the specific host for movement and to counter host defense systems (Dung, 2006; Lucas, 2006). Viruses that infect higher plants share a number of common principles with animal viruses. These include virion morphology and strategies for replication and expression of their genomes. Though, to establish a productive infection in the host, plant virus need to be able to move throughout a plant from an initially infected cell (Yokomi et al., 2017). Success depends upon compatible interactions between viral and host factors. Generally, systemic movement is thought to involve two distinct processes: cell-to-cell movement which indicates the process that allows the virus to transverse the Abstract: The genuses Citrus are commercially important fruit crop belongs to Rue family. They are mainly cultivated in the subtropical and tropical regions of the world between 40 0 north and south latitude in over 137 countries. However, citrus production has been delayed with biotic and a biotic factors. Mainly, plant viruses are highly prevalent and serious threat to cultivated plants and agricultural production in plants like vegetables and fruits worldwide. Citrus triteza virus (CTV), is the largest and most complex member of the genus Closter virus (family Closteroviridae) that induce the most destructive disease of cultivars and hybrids of citrus worldwide. The only natural non-citrus host that has been reported is Passilora. Natural hosts of CTV remain essentially symptomless when infected by most CTV isolates. To establish a productive infection in a host plant virus needs to be able to move throughout the plant from an initially infected cell. The spatial and temporal spread of CTV in citrus orchards ha...