PROPOSED REVISION OF NOMENCLATURE FOR POTYVIRUS RESISTANCE GENES IN CAPSICUM

As knowledge of the genetic resources available for disease resistance in crop plants increases, the development of conventions for naming d isease resistance loci that can be applied consistently across plant s pecies and pathogens becomes increasingly important. Resistance gene d esignations have not followed regular conventions, exemplified by the locus and allele designations for resistance to three potyviruses: pot ato virus Y (PVY), tobacco etch virus (TEV) and pepper mottle virus (P epMoV) in Capsicum spp. To further complicate the situation, no system of nomenclature has been proposed that directly reflects the genetic associations (linkage, pleiotropy) commonly observed between resistanc e to distinct viral pathogens. In some cases, the locus designations c ompletely obscure the possible relationship or identity among the resi stance genes. We propose a nomenclature that clarifies the genetic and biological relationships among potyvirus resistance genes in pepper, and should represent a generally useful scheme for other crops and pat hogen groups. Further, it avoids the need for revision of gene symbols due to taxonomic changes of host or pathogen. As a general rule, we p ropose the symbol pvr for (p) under bar oty (v) under bar irus resista nce locus, followed by a number specific to each locus, according to t he chronological order in which they were identified. Alleles at each locus will be differentiated using numerical superscripts. At present, there is clear evidence for four independent loci in Capsicum, each w ith alleles that confer resistance to viral isolates that belong to on e or more of the viruses, PVY, PepMoV and TEV. When resistance to more than one potyvirus is attributed to a factor or factors that are iden tical or very thightly linked, the factor(s) that control that resista nce will be given one symbol until it is clearly demonstrated that the re are distinct alleles and/or loci involved at which time a new allel e and/or locus designation will be made with the next highest availabl e number.