Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Rodrigo Alberto Valverde


Ten potyvirus isolates from sweet potato (Ipomoea batatas) cv. Beauregard showing russet crack symptoms and three other isolates associated with internal cork and feathery mottle symptoms were obtained from commercial fields in the United States. The biological properties of these isolates and those of a mechanically transmitted virus obtained from I. purpurea were compared with a previously characterized sweet potato feathery mottle virus strain (SPFMV-C) from North Carolina. The symptoms induced in a range of hosts indicated that two of the isolates were associated with russet crack symptoms in the cultivar Jersey; however, none of them could be associated with russet-crack in 'Beauregard'. Reverse transcription polymerase chain reaction (RT-PCR) based protocols were tested in order to evaluate their applicability for sweet potato virus detection. Results suggested that RT-PCR is an efficient method for molecular characterization of sweet potato viruses without the need for virus purification. However, it was inconsistent for routine diagnosis. Using a combination of primers (Pot1-Pot2 and Pot2-P89), conserved regions of 14 isolates were amplified, except the virus obtained from I. purpurea. The RT-PCR product from three isolates including SPFMV-C were cloned and sequenced. Comparison of the 5$\sp\prime$ coat protein coding region nucleotide sequence of these isolates with those of other isolates stored in GeneBank revealed high degree of homology between SPFMV-952 and SPFMV-RC and between SPFMV-956 and SPFMV-C. Restriction fragment length polymorphism and single strand conformational polymorphism analysis of the cDNA of selected isolates did not reveal genomic differences that could be linked to different biological properties. Enzyme-linked immunosorbent assay tests using monoclonal antibodies specific for potyviruses detected the presence of potyviruses in symptomatic plants.