title: In situ embryo rescue for generation of wide intra- and interspecific hybrids of Panicum virgatum L.
abstract: Wide crosses have been used for decades as a method for transferring novel genetic material and traits in plant breeding. Historically, many products of wide crosses require tedious and inefficient surgical embryo rescue prior to embryo abortion to recover single plantlets. We have utilized transgenic switchgrass (Panicum virgatum L. cv Alamo) as a pollen donor in conjunction with antibiotic or herbicide selection for recovery of intra-and interspecific F1crosses by using developing ovules from the female parent and selecting for embryogenic cultures derived from the in situ immature embryo. Using this approach, several intravarietial crosses were generated between transgenic Alamo and the switchgrass varieties Kanlow, Blackwell and Cave-in-Rock as well as an interspecific cross with Atlantic coastal panicgrass. This procedure selected F1embryogenic callus produced from the developing embryo contained within isolated immature ovules. Several clonal plants were successfully regenerated from each cross. Southern blot, PCR, phenotypic analyses and genomic analysis confirmed F1hybrids. Using genotyping-by-sequencing shows the hybridization of the recovered plants by determining the ratio of transgressive markers to total compared markers between parents and their potential offspring. The ratio of transgressive markers to total compared markers was significantly lower between parents and their predicted offspring than between parents and offspring unrelated to them. This approach provides the possibility to move useful transgenes into varieties that are recalcitrant to direct transformation which can be optionally segregated thus useful to create new hybrids, as well as recovery of wide crosses that are either difficult or impossible using traditional techniques.
authors.affiliation: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, USA. apkausch@uri.edu.
authors.forename: Albert P
authors.initials: AP
authors.lastname: Kausch
authors.affiliation: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Tilelli
authors.affiliation: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Hague
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Heffelfinger
authors.affiliation: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, USA.
authors.forename: David
authors.initials: D
authors.lastname: Cunha
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Moreno
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Dellaporta
authors.affiliation: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Nelson
mesh_terms: D001947:Breeding; D003433:Crosses, Genetic; D005838:Genotype; D006824:Hybridization, Genetic; D008897:Panicum / Q000196:embryology / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000502:physiology
keywords: genetic transformation; switchgrass; tissue culture; transgenic plants; wide crosses