title: Somatic hybridization for citrus rootstock breeding: an effective tool to solve some important issues of the Mediterranean citrus industry.
abstract: The prevalence of sour orange rootstock in the southern and eastern part of the Mediterranean Basin is presently threatened by the spread of Citrus Tristeza Virus (CTV) and its main vector Toxoptera citricida, combined with abiotic constraints such as drought, salinity and alkalinity. The search for alternative CTV-resistant rootstocks that also withstand the other constraints is now considered an urgent priority for a sustainable citrus industry in the area. Complementary progenitors can be found in citrus germplasm to combine the desired traits, particularly between Poncirus and Citrus genera. The production of somatic hybrids allows cumulating all dominant traits irrespective of their heterozygosity level, and would appear to be an effective way to solve the rootstock challenge facing the Mediterranean citrus industry. This paper presents the results obtained during a regional collaborative effort between five countries, to develop new rootstocks by somatic hybridization. New embryogenic callus lines to be used for somatic hybridization have been created. Protoplast fusions have been performed at CIRAD and IVIA laboratories, focusing on intergeneric combinations. Analysis of ploidy level by flow cytometry and molecular markers confirmed the acquisition of new interesting tetraploid somatic hybrids for six combinations. Diploid cybrids with intergeneric (Citrus × Poncirus) nucleus and C. reticulata or C. aurantifolia mitochondria were also identified for four combinations. The agronomical performance of a pre-existing somatic hybrid between Poncirus trifoliata and Citrus reticulata was validated in calcareous soils in Morocco. Somatic hybridization is now integrated into the breeding programs of the five Mediterranean countries.
authors.affiliation: UPR 75, Département BIOS, CIRAD, Av. Agropolis, TA A-75/02, 34398, Montpellier Cedex 5, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Dambier
authors.forename: Hamid
authors.initials: H
authors.lastname: Benyahia
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pensabene-Bellavia
authors.forename: Yildiz
authors.initials: Y
authors.lastname: Aka Kaçar
authors.forename: Yann
authors.initials: Y
authors.lastname: Froelicher
authors.forename: Zina
authors.initials: Z
authors.lastname: Belfalah
authors.forename: Beniken
authors.initials: B
authors.lastname: Lhou
authors.forename: Najat
authors.initials: N
authors.lastname: Handaji
authors.forename: Bruno
authors.initials: B
authors.lastname: Printz
authors.forename: Raphael
authors.initials: R
authors.lastname: Morillon
authors.forename: Turgut
authors.initials: T
authors.lastname: Yesiloglu
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
authors.forename: Patrick
authors.initials: P
authors.lastname: Ollitrault
mesh_terms: D000818:Animals; D001042:Aphids / Q000821:virology; D001947:Breeding; D002459:Cell Fusion; D002957:Citrus / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D017790:Closterovirus / Q000472:pathogenicity; D003470:Culture Media; D005602:France; D005638:Fruit / Q000235:genetics / Q000254:growth & development; D005819:Genetic Markers; D006822:Hybrid Cells; D006824:Hybridization, Genetic / Q000235:genetics; D009018:Morocco; D010935:Plant Diseases / Q000276:immunology / Q000517:prevention & control / Q000821:virology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development; D058439:Plant Somatic Embryogenesis Techniques / Q000379:methods*; D011003:Ploidies; D032104:Poncirus / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D011523:Protoplasts / Q000166:cytology; D012038:Regeneration; D013030:Spain; D014416:Tunisia; D014421:Turkey
chemical_list: D003470:Culture Media; D005819:Genetic Markers