Deployment And Characterization Of Recessive Resistance Gene Pvr1 In The Solanaceae

Abstract

Potyviruses are the largest group of plant viruses and can infect pepper, potato and tomato which were the focus of this dissertation. Pepper resistance to potyviruses has been attributed to point mutations at the pvr1 locus which cause conformational shifts in encoded protein eukaryotic translation initiation factor eIF4E. In addition to susceptible allele Pvr1 exp(+), three pvr1 resistance alleles were the focus of this study: pvr1, pvr1 exp(1), pvr1 exp(2). Resistance conferred by these three pvr1 alleles has been linked to the inability for eIF4E to interact with the viral encoded protein VPg, a protein covalently bound to the 5' end of the potyvirus genome. To determine if VPg was the virulence determinant for two strains of Tobacco etch virus (TEV), two VPg viral chimera were synthesized using a PCR based domain swapping method which we developed. The technique is a versatile and widely applicable alternative to conventional restriction enzyme digestion and ligation methods and is a valuable tool for determining which domains of a viral genome are essential for infectivity. Substituting VPg from an infectious TEV strain was found to determine the outcome of host infection for both pvr1 and pvr12. In additional studies, we transformed widely cultivated potato variety Russet Burbank with one of the four pepper pvr1 alleles to confer resistance to potyvirus Potato virus Y (PVY). Russet Burbank lines which overexpressed the pvr1 exp(2) or the pvr1 exp(1) allele from pepper were resistant to at least one of three PVY strains tested. The majority of pvr1 exp(2) lines were resistant to all strains of PVY and plants grown from tubers of the inoculated resistant lines were virus free