naa a22 4500 510730299 CHVBK 20180411082950.0 cr unu---uuuuu 180411e20130201xx s 000 0 eng 10.1007/s11295-012-0555-y doi (NATIONALLICENCE)springer-10.1007/s11295-012-0555-y Barriers to interspecific hybridization between Juglans nigra L. and J [Elektronische Daten] regia L species [Paola Pollegioni, Irene Olimpieri, Keith Woeste, Giovanni De Simoni, Maria Gras, Maria Malvolti] Juglans nigra and Juglans regia are phylogenetically divergent species. Despite the economic interest in Juglans × intermedia (J. nigra ×  J. regia), walnut hybridization is rare under natural conditions and still difficult using controlled pollination. Here, we evaluated some reproductive mechanisms that may prevent successful natural hybridization. The study of flowering phenology of 11 J. nigra and 50 J. regia trees growing in a plantation provided information regarding the opportunity for interspecific crosses. Variation in flower size, pollen quality of putative donors, and variation in seed yield and rate of hybrid production among putative maternal trees were examined. DNA fingerprinting and parentage analyses based on nine microsatellites permitted the identification of hybrids and hybridogenic parent. Our data indicated that overlap occurred between the staminate flowering of protogynous J. regia and the beginning of pistillate flowering of protogynous J. nigra. Differences in floral size were computed between walnut species. Only three hybrids among 422 offspring of eleven J. nigra progenies were identified. Interspecific hybridization involving pollination of one early-flowering-protogynous J. nigra by three protogynous J. regia trees was detected. The correct development of J. regia male gametophytes, high pollen viability (86.5%), and germination (57.6%) ruled out the possibility that low pollen quality contributed to depressed hybrid production. Our findings indicated that these two species tended to remain reproductively isolated. The substantial disjunction in flowering time and additional prezygotic barriers such as differences in floral size and conspecific pollen advance may affect interspecific gene flow between J. regia and J. nigra. Springer-Verlag, 2012 Walnut hybridization nationallicence SSR fingerprinting nationallicence Prezygotic barriers nationallicence Bloom synchrony nationallicence Conspecific pollen advance nationallicence Floral differences nationallicence Pollegioni Paola C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut Olimpieri Irene C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut Woeste Keith U.S.D.A. Forest Service, Hardwood Tree Improvement and Regeneration Center, Department of Forestry and Natural Resources, Purdue University, 715 West State Street, 47907-2061, West Lafayette, IN, USA aut De Simoni Giovanni C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut Gras Maria C.R.A—Research Unit for Wood Production Outside Forests, Via Valle della Quistione 27, 00166, Rome, Italy aut Malvolti Maria C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut Tree Genetics & Genomes Springer-Verlag 9/1(2013-02-01), 291-305 1614-2942 9:1<291 2013 9 11295 https://doi.org/10.1007/s11295-012-0555-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11295-012-0555-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pollegioni Paola C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut NATIONALLICENCE 700 1- Olimpieri Irene C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut NATIONALLICENCE 700 1- Woeste Keith U.S.D.A. Forest Service, Hardwood Tree Improvement and Regeneration Center, Department of Forestry and Natural Resources, Purdue University, 715 West State Street, 47907-2061, West Lafayette, IN, USA aut NATIONALLICENCE 700 1- De Simoni Giovanni C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut NATIONALLICENCE 700 1- Gras Maria C.R.A—Research Unit for Wood Production Outside Forests, Via Valle della Quistione 27, 00166, Rome, Italy aut NATIONALLICENCE 700 1- Malvolti Maria C.N.R. Institute of Agro-environmental and Forest Biology, viale Marconi 2, 05010, Porano, Terni, Italy aut NATIONALLICENCE 773 0- Tree Genetics & Genomes Springer-Verlag 9/1(2013-02-01), 291-305 1614-2942 9:1<291 2013 9 11295 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer