title: Recovery and characterization of a Citrus clementina Hort. ex Tan. 'Clemenules' haploid plant selected to establish the reference whole Citrus genome sequence.
abstract: BACKGROUND
  In recent years, the development of structural genomics has generated a growing interest in obtaining haploid plants. The use of homozygous lines presents a significant advantage for the accomplishment of sequencing projects. Commercial citrus species are characterized by high heterozygosity, making it difficult to assemble large genome sequences. Thus, the International Citrus Genomic Consortium (ICGC) decided to establish a reference whole citrus genome sequence from a homozygous plant. Due to the existence of important molecular resources and previous success in obtaining haploid clementine plants, haploid clementine was selected as the target for the implementation of the reference whole genome citrus sequence.
  
  
  RESULTS
  To obtain haploid clementine lines we used the technique of in situ gynogenesis induced by irradiated pollen. Flow cytometry, chromosome counts and SSR marker (Simple Sequence Repeats) analysis facilitated the identification of six different haploid lines (2n = x = 9), one aneuploid line (2n = 2x+4 = 22) and one doubled haploid plant (2n = 2x = 18) of 'Clemenules' clementine. One of the haploids, obtained directly from an original haploid embryo, grew vigorously and produced flowers after four years. This is the first haploid plant of clementine that has bloomed and we have, for the first time, characterized the histology of haploid and diploid flowers of clementine. Additionally a double haploid plant was obtained spontaneously from this haploid line.
  
  
  CONCLUSIONS
  The first haploid plant of 'Clemenules' clementine produced directly by germination of a haploid embryo, which grew vigorously and produced flowers, has been obtained in this work. This haploid line has been selected and it is being used by the ICGC to establish the reference sequence of the nuclear genome of citrus.
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Ctra, Moncada-Náquera km 4,5, 46113 Moncada, Valencia, Spain. aleza@ivia.es
authors.forename: Pablo
authors.initials: P
authors.lastname: Aleza
authors.forename: José
authors.initials: J
authors.lastname: Juárez
authors.forename: María
authors.initials: M
authors.lastname: Hernández
authors.forename: José A
authors.initials: JA
authors.lastname: Pina
authors.forename: Patrick
authors.initials: P
authors.lastname: Ollitrault
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
mesh_terms: D001947:Breeding; D032461:Chromosomes, Plant; D002957:Citrus / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D005819:Genetic Markers; D018745:Genome, Plant; D006238:Haploidy; D018895:Microsatellite Repeats; D011058:Pollen / Q000235:genetics
chemical_list: D018744:DNA, Plant; D005819:Genetic Markers
references.citation: Nature. 2007 Sep 27;449(7161):463-7
references.pmid: 17721507
references.citation: BMC Genomics. 2008 Jun 16;9:287
references.pmid: 18558001
references.citation: Theor Appl Genet. 1982 Dec;62(4):295-300
references.pmid: 24270646
references.citation: Mol Ecol Resour. 2008 Jan;8(1):119-22
references.pmid: 21585732
references.citation: BMC Genomics. 2008 Sep 18;9:423
references.pmid: 18801166
references.citation: Theor Appl Genet. 1996 Apr;92(5):599-609
references.pmid: 24166329
references.citation: J Integr Plant Biol. 2008 Aug;50(8):941-50
references.pmid: 18713343
references.citation: Genome Res. 2005 Aug;15(8):1127-35
references.pmid: 16077012
references.citation: Plant Mol Biol. 2003 Mar;51(5):703-18
references.pmid: 12678558
references.citation: BMC Plant Biol. 2008 Jun 13;8:66
references.pmid: 18554400
references.citation: Mol Gen Genet. 1996 Mar 7;250(4):405-13
references.pmid: 8602157
references.citation: Genetics. 2007 Aug;176(4):2055-67
references.pmid: 17565939
references.citation: Trends Plant Sci. 2007 Aug;12(8):368-75
references.pmid: 17629539
references.citation: BMC Genomics. 2008 Jul 03;9:318
references.pmid: 18598343
references.citation: Plant Cell Rep. 2007 Jul;26(7):937-44
references.pmid: 17318461
references.citation: Int J Plant Genomics. 2008;2008:528361
references.pmid: 18509486
references.citation: Mol Genet Genomics. 2001 Apr;265(2):302-10
references.pmid: 11361341
references.citation: Theor Appl Genet. 1993 Oct;87(1-2):229-32
references.pmid: 24190217
references.citation: BMC Genomics. 2007 Jan 25;8:31
references.pmid: 17254327
references.citation: Plant Mol Biol. 2005 Feb;57(3):375-91
references.pmid: 15830128
references.citation: Genetics. 2000 Jan;154(1):397-412
references.pmid: 10628998