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A diploid backcross population derived from a cross between Solanum tuberosum and Solanum berthaultii segregated for monogenic dominant hypersensitivity to Potato virus Y (PVY). We propose the symbol Nytbr for this locus because plants carrying this gene develop necrosis after inoculation with PVY and the allele originated in S. tuberosum. The gene mapped to chromosome IV between TG316 and TG208 at LOD=2.72. This location does not correspond to any other mapped resistance genes in potato. [ABSTRACT FROM AUTHOR]

Potato viruses are prevalent worldwide and cause substantial economical losses in the potato crop (Solanum tuberosum L.). Therefore, various types of resistance to potato viruses identified in cultivated and wild potato species are used in potato breeding programs and are briefly reviewed in this paper. However, the current nomenclature of virus resistance specificities is confusing because it was adopted at an earlier time when several virus strain groups were believed to represent individual virus species and because it does not distinguish between strain-specific and comprehensive resistance specificities. A consistent nomenclature is desirable to distinguish both currently known virus resistances and any novel virus resistances detected in the future. A descriptive and systematic nomenclature for resistance specificities is proposed which denotes (1) type of resistance (2) identity of virus (3) the virus strain group(s) against which the resistance is effective (4) the virus strain group(s) against which the resistance is not effective, and (5) the potato species in which the resistance is described. [ABSTRACT FROM AUTHOR]

Resistance to potato viruses was examined in the F1 hybrids (TET) obtained from a cross between a diploid (2n = 24), tuber-bearing inter-specific hybrid 87HW13.7 (Solanum tuberosum W231 × S. multidissectum PI 473354) and a diploid (2n = 24), nontuber-bearing wild potato species (S. brevidens CPC 2451) using S. phureja IvP35 (2n = 24) for rescue pollination. The parental plants were susceptible to PVX, whereas two hybrids (TET38.2 and TET38.9) and S. phureja IvP35 reacted with hypersensitivity to PVX. Two hybrids (TET 38.9 and TET 38.12) were extremely resistant to PVY0, which was similar to S. brevidens and S. phureja IvP35, whereas the remaining two hybrids were moderately resistant to PVY0. No resistance to PVA and PLRV was observed in the progenies, in contrast to S. brevidens which was extremely resistant to PVA and PLRV. Hypersensitivity to PVX in two progenies suggested (1) integration by somatic translocation or heterofertilization and expression of genes from the rescue pollinator S. phureja IvP35, or (2) transgressive or complementary gene action. [ABSTRACT FROM AUTHOR]

In vitro cultures of potato (Solanum tuberosum cv. Papa Amarillo) were imported into the United States and were subjected to routine pathogen screening for newly introduced varieties. These cultures indexed positive for several of the six viruses tested and thus were treated using standard methods for eliminating viruses in in vitro cultures. Although the therapy apparently freed the potato of the tested viruses, some of the cultures continued to exhibit mosaic symptoms when planted in the greenhouse. When examined by electron microscopy, these plants contained flexuous rods. Tested samples did not index positive with any potato virus-specific polyclonal antisera but reacted with the ’universal’ potyvirus monoclonal antibody. These results indicated that these samples were likely infected with an as yet undescribed potyvirus. Further investigation indicated that this virus is a new strain of Potato virus V (PVV) that is serologically distinct from the common strain. This is the first description of a distinct strain of PVV. This particular strain has diverged sufficiently from other isolates of PVV to no longer be detectable by some commonly used antisera, and therefore is a concern for the future restriction of PVV spread into regions of the world where it is not currently present. [ABSTRACT FROM AUTHOR]