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1、RESEARCH ARTICLEMorphological, molecular and statistical tools to identify Castanea species and their hybridsJ. Ferna ndez-CruzJ. Ferna ndez-Lo pezReceived: 30 April 2012/Accepted: 29 August 2012/Published online: 15 September 2012 ? Springer Science+Business Media B.V. 2012AbstractThe aim of this s
2、tudy was to investigate, in rela- tion to reference samples, the genetic structure of several natural Castanea populations of unknown origin and of hybrids from the clone collection of the Louriza n Forest ResearchCenter.Atotalof115individualssampledfromfour Castanea sativa stands located in the nor
3、thwest of Spain, 61 Castanea crenata individuals and 27 Castanea mollissimaindividualswereclassifiedonthebasis offourmorphologicaltraits,andgenotypedwith11microsatellitelocitodefineaset of reference samples. The data analyzed with the program STRUCTURE detected four clusters: the two Asiatic species
4、 and two clusters in C. sativa. From these reference samples, pure individuals and hybrids of known genealogy were sim-ulated to determine the efficiency with which STRUCTURE and NEWHYBRIDS assigned them to pure or hybrid groupsandtoaspecificgenealogicalclass,respectively.Asexpected, the discriminat
5、ion and assignment of the simulated individu- als improved with increasing Fstvalue. The two clustersidentifiedwithinC.sativamaycorrespond togenepools withdifferent adaptive characteristics previously identified in provenance tests; pure and admixed populations of both C.sativa gene pools were ident
6、ified.KeywordsChestnut ? Microsatellite ? Hybrids ? Reference samples ? Assignment ? Genealogical classAbbreviations BC(Cc)Backcross to Castanea crenata BC(Cm)Backcross to Castanea mollissima BC(Cs)Backcross to Castanea sativaBC(NCs)Backcross to Northern cluster of Castanea sativa BC(SCs)Backcross t
7、o Southern cluster of Castanea sativa CcCastanea crenata CmCastanea mollissima FstInbreeding coefficient F1First filial generation F2Second filial generation KNumber of clusters LnP(K)Posterior probability of the data for a given K NNumber of individuals NCsNorthern cluster of Castanea sativa PCRPol
8、ymerase chain reaction SCsSouthern cluster of Castanea sativa DKAn ad hoc quantity based on the second-order rate of change of the likelihood function with respect to K pType of prior in use for the mixing proportions in NEWHYBRIDS hType of prior in use for the allele frequencies in NEWHYBRIDSIntrod
9、uctionSweet chestnut (Castanea sativa Mill.) is widely distrib- uted across the Mediterranean region from the Caspian Sea to the Atlantic Ocean; large areas of its distribution are located in Northern and Northwestern Spain together with several discontinuous patches in Central-Western Spain and the
10、 Andalusian mountains (Ferna ndez-Lo pez and Monteagudo 2010). The genetic structure of wild Spanish populations shows high levels of genetic diversityJ. Ferna ndez-Cruz ? J. Ferna ndez-Lo pez (flushing time is correlated with resistance to spring frostand could also reflect adaptations to drought (
11、Ferna ndez- Lo pez et al. 2005a). Sweet chestnut has been exploited by humans for cen- turies. Historical evidence indicates that it has been used in Spain since medieval times (Conedera et al. 2004). Grafted selections have been grown in orchards for the valuable nuts or in coppices for wood produc
12、tion. Since the eigh- teenth century, the ink disease induced by Phytophthora cinnamomi Rands caused mortality in Northern Spain. The blight fungus, Cryphonectria parasitica Murrill, also has affected Galician chestnut populations in recent decades. Owing to the sensitivity of sweet chestnut to thes
13、e diseases, Japanese chestnut (Castanea crenata Blume) and Chinese chestnut (Castanea mollissima Sieb. et Zucc.) were intro- duced to Europe in the early twentieth century and crossed with sweet chestnut to produce hybrids with resistance tothese two pathogens; specifically, from 1920 to 1960, Asiat
14、ic germplasm was introduced to the NorthwesternIberian Peninsula (Ferna ndez-Lo pez 2011). The flowering period of the Asiatic species and sweet chestnut overlaps slightly, therefore introgression of Asiatic germplasm intosweet chestnut populations is possible. Artificial hybrids between C. sativa a
15、nd the Asiatic species were produced by Galla stegui(1926)andUrquijo-Landaluze(1957)in Northwestern Spain in areas with an Atlantic climate, and clonal plantations have been developed mainly since 1960. In 1989, the Louriza n Forest Research Center initiated aprogram for identification, clonal propa
16、gation and selection of clones resistant to Phytophthora spp. for timber pro- duction (Ferna ndez-Lo pez et al. 1992, 1995, 2008; Mir- anda-Fonta n aandFerna ndez-Lo pez2001,Miranda- Fonta n a et al. 2007). Consequently, a total of 32 clones from the clone collection located at the Louriza n Forest Research Center have been approved as basic material forchestnut timber production (BOLETIN OFICIAL DEL ESTADO 2007). Presently, two programs for the conservation of sweet
