Transfer of resistance to PLRV titer buildup from Solanum etuberosum to a tuber-bearing Solanum gene pool

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Abstract
Hybrids between Solanum etuberosum and S. pinnatisectum harboring resistance to titer buildup of potato leafroll virus (PLRV) were reciprocally crossed with tuber-bearing wild species S. acaule and S. verrucosum. A total of 47 hybrids with acaule were obtained with the aid of embryo rescue and sterile culturing of embryos from imbibing seeds. All but two hybrids with acaule had low pollen stainabilities or were pollen sterile. Hybrid seeds from crosses with verrucosum were easily obtained, and the triploid progenies were sterile. Hybrid progeny were screened for resistance to PLRV infection by viruliferous green peach aphid and for resistance to titer buildup. Although hybrids did not exhibit resistance to infection, PLRV was not detectable using ELISA. Virus was detected, however, by graft transmission to Datura stramonium. Crosses of fertile acaule-etuberosum-pinnatisectum hybrids with S. phureja, a cultivated diploid, using the latter as pollen parent, produced berries but seed did not complete development and was aborted. Rescue of immature embryos 25 days after pollination by excision from berries and sterile culture produced vigorous, pot-cultured plants. Segregation of susceptible (virus detected) and resistant (virus undetected) progenies suggests simple inheritance.