Abstract

Statement of the Problem: Infectious clones are important tools for understanding viral pathogenesis which can allow for development of appropriate viral control strategies. Infectious clones can also be used as a uniform viral source for testing breeding lines. For cassava brown streak virus, there has been a lack of infectious clones which has limited the potential to effectively understand the viral pathogenesis mechanism of this virus. The purpose of this work was to construct full-length infectious clones of Ugandan cassava brown streak virus. The infectious clones are to subsequently be used in screening cassava breeding lines for resistance to the virus. In addition, the infectious clones are to act as very important tools in understanding the variations in viral pathogenicity including differences in symptoms observed with the different strains of the virus. Methodology & Theoretical Orientation: The yeast homologous technique was used to reconstruct the UCBSV genome in the backbone p YES2 vector. Yeast homologous recombination allows joining together of segments of DNA with overlapping sequences through recombination and the resultant product is the complete genome of the virus cloned inside a backbone vector. An SP6 promoter was introduced at the 5’end of the genome to allow for invitro transcription. Findings: The UCBSV infectious clone was successfully constructed and the genome of the infectious clone sequenced. The infectious clone was found to infect both the model host plants N. benthamiana and the target cassava plant. The infections caused by the generated infectious clones were similar to those caused by the wild type UCBSV virus. Conclusion & Significance: This work has provided the first report on the construction of full length infectious clones of UCBSV virus. The infectious clones are further going to be very useful tools in understanding UCBSV viral pathogenicity and hence guide in the control of the virus.