Abstract
Date palm, Phoenix dactylifera L., is one of the oldest domesticated plants, but research to understand its diversity, evolution and adaptability is still lagging behind. One of the major limitations has been the lengthy life-cycle of this plant. Meanwhile, breeding challenges and opportunities are enormous, which in turn highlights the importance of how unraveling the evolutionary driving forces of this desert crop could help preserve its socio-economical, botanical and nutritional values. This review represents an up-to-date account of date palm progress in terms of genetics and breeding and underlines the challenges facing these two fields of research in this special crop. It also highlights some of the opportunities on the rise for breeding in this crop.
Keywords
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Ahloowalia BS, Maluszynski M, Nichterlein K (2004) Global impact of mutation-derived varieties. Euphytica 135:187–204
Al Khalifah NS, Askari E (2003) Molecular phylogeny of date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia by DNA fingerprinting. Theor Appl Genet 107:1266–1270
Al Mansoori TA, Alaa El-Deen MN, Caligari PDS (2007) Evaluation of in vitro screening techniques for salt tolerance in date palm. Acta Hortic 736:301–307
Al-Ayedh H (2008) Evaluation of date palm cultivars for rearing the red date palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae). Fla Entomol 91:353–358
Al-Dous EK, George B, Salameh YM et al (2009) Qatar researchers sequence draft version of date palm genome. URL: http://qatar-weill.cornell.edu/research/datepalmGenome/download.html
Al-Khayri JM (2001) Optimization of biotin and thiamine requirements for somatic embryogenesis of date palm (Phoenix dactylifera L.). In Vitr Cell Dev Biol Plant 37:453–456
Al-Khayri JM (2002) Growth, praline accumulation, and ion content in NaCl-stressed callus cultures of date palm (Phoenix dactylifera L.). In Vitr Cell Dev Biol Plant 38:79–82
Al-Khayri JM (2003) In vitro germination of somatic embryos in date palm: effect of auxin concentration and strength of MS salts. Curr Sci 84:101–104
Al-Khayri JM (2005) Date palm Phoenix dactylifera L.. In: Jain SM, Gupta PK (eds) Protocols of somatic embryogenesis in woody plants. Springer, Berlin, pp 309–320
Al-Khayri JM (2007) Date palm Phoenix dactylifera L. micropropagation. In: Jain SM, Häggman H (eds) Protocols for micropropagation of woody trees and fruits. Springer, Dordrecht, pp 509–526
Al-Khayri JM, Al-Bahrany AM (2001) Silver nitrate and 2-isopentyladenine promote somatic embryogenesis in date palm (Phoenix dactylifera L.). Sci Hortic 89:291–298
Al-Khayri JM, Al-Bahrany AM (2004a) Genotype-dependent in vitro response of date palm (Phoenix dactylifera L.) cultivars to silver nitrate. Sci Hortic 99:153–162
Al-Khayri JM, Al-Bahrany AM (2004b) Growth, water content, and proline accumulation in drought-stressed callus of date palm. Biol Plant 48:105–108
Allard RW (1956) Formulas and tables to facilitate the calculation of recombination values in heredity. Hilgard 24:235–278
Al-Ruqaishi IA, Davey M, Alderson P, Mayes S (2008) Genetic relationships and genotype tracing in date palms (Phoenix dactylifera L.) in Oman based on microsatellite markers. Plant Genet Res 61:70–72
Al-Salih AA, Al Rawi A (1987) A study of the cytology of two female cultivars of date palm. Date Palm J 5:123–124
Al-Salih AA, Al-Jarrah A (1987) Chromosome number of a date palm male: cultivar Ghannami Akhdar. Date Palm J 5:128–133
Al-Salih AA, Al-Najjar NR, Al-Mashhadani AN (1987) A study on the chromosome number of two specific female date palm cultivars. Date Palm J 5:134–143
Al-Wasel ASAA (2005) Survey study on somaclonal variations in in vitro-derived date palm trees. In: Proceeding of the international workshop on true-to-typeness of date palm tissue culture-derived plants, Institut National de Recherche Agronomique, Morocco, 23–25 May 2005. http://www.inra.org.ma/ist/publications/ouvrages/truetype.pdf
Azequour M, Majourhat K, Baaziz M (2002) Morphological variations and isoenzyme polymorphism of date palm clones from in vitro culture acclimatized and established on soil in South Morocco. Euphytica 123:57–66
Baaziz M (2000) Date palm culture in the Maghreb countries: constraints and scientific research. In: Proceedings of the date palm international symposium. Namibia, 22–25 Feb 2000, pp 306–311
Baenziger PS, Peterson CJ (1992) Genetic variation: its origin and use for breeding self-pollinated species. In: Stalker TM, Murphy JP (eds) Plant breeding in the 1990s. Proceedings symposium on plant breeding in the 1990s, Raleigh, March 1991. CAB International, Wallingford, pp 69–92
Baker WJ, Asmussen CB, Barrow SC et al (1999) A phylogenetic study of the palm family (Palmae) based on chloroplast DNA sequences from the trnL - trnF region. Plant Syst Evol 219:111–126
Barrow S (1998) A monograph of Phoenix L. (Palmae: Coryphoideae). Kew Bull 53:513–575
Beal JM (1937) Cytological studies in the genus Phoenix. Bot Gaz 99:400–407
Beauchesne G (1983) Vegetative propagation of date palm (Phoenix dactylifera) by in vitro culture. In: Proceedings of the first symposium of date palm. King Faisal University, Al-Hassa, Saudi Arabia, 23–25 March 1982, pp 698–699
Beauchesne G, Zaid A, Rhiss A (1986) Meristematic potentialities of bottom of young leaves to rapidly propagate date palm. In: Proceeding of second symposium of date palm vol 1. King Faisal University, Al-Hassa, 3–6 March 1986, pp 87–93
Beccari O (1890) Revista monografica delle species del genera Phoenix L. Malesia 3:345–416
Bekheet SA, Saker MM, Taha HS, Moursy HA (2001) Plant regeneration via somatic embryogenesis of date palm (Phoenix dactylifera L.). Arab J Biotechnol 4:111–118
Bekheet SA, Taha HS, Saker MM, Moursy HA (2002) A synthetic seed system of date palm through somatic embryos encapsulation. Annu Agric Sci Ain Shams Univ Cairo 47:325–337
Ben Abdallah A, Lepoivre P (2000) Production of date palm (Phoenix dactylifera L.) fruit and diploid embryos following gibberillic acid treatment of unpollinated female influorescences. Cah Agric 9:467–473
Ben Abdallah A, Stiti K, Lepoivre P, du Jardin P (2000) Date palm cultivar identification using random polymorphic DNA RAPD markers identification. Cah Agric 9:103–107
Ben Abdallah A, Lepoivre P, du Jardin P (2001) Apomixis induction possibility explored in date palm (Phoenix dactylifrea L.), In: Proceedings second international conference on date palms. Al-Ain, UAE, 25–27 March 2001, pp 164. URL: http://www.pubhort.org/datepalm/index2.htm
Benbadis BK (1992) Coconut and date palm. In: Hammerschlag FA, Litz RW (eds) Biotechnology of perennial fruit crops. CAB International, Wallingford, pp 383–400
Bernardo R (2001) What if we knew all the genes for a quantitative trait in hybrid crops? Crop Sci 41:1–4
Bernardo R (2002) Breeding for quantitative traits in plants. Stemma Press, Woodbury
Bhaskaran S, Smith RH (1992) Somatic embryogenesis from shoot tip and immature inflorescence of Phoenix dactylifera cv. Barhee. Plant Cell Rep 12:22–25
Carpenter JB, Ream CL (1976) Date palm breeding, a review. Date Grow Inst 53:25–33
Collard BCY, Jahufer MZZ, Brouwer JB, Pang ECK (2005) An introduction to markers, quantitative trait loci (QTL) mapping and marker-assisted selection for crop improvement: the basic concepts. Euphytica 142:169–196
Cushman JC, Bohnert HJ (2000) Genomic approaches to plant stress tolerance. Curr Opin Plant Biol 3:117–124
Daayf F, El Bellaj M, El Hassni M et al (2003) Elicitation of soluble phenolics in date palm (Phoenix dactylifera) callus by Fusarium oxysporum f. sp. albedinis culture medium. Environ Exp Bot 49:41–47
Djerbi M (2000) Abnormal fruiting of the date palm trees derived from tissue culture. In: Proceedings of date palm international symposium. Windhoek, Namibia. 22–25 Feb 2000, p 73
El Bellaj M, El Jaafari S, El Hadrami I (2000) L’AIA-oxydase marqueur et régulateur potentiel de l’embryogenèse somatique chez Phoenix dactylifera L. Cah Agri 9:193–195
El Hadrami I (1995) L’embryogenèse somatique chez Phoenix dactylifera L. quelques facteurs limitants et marqueurs biochimiques. Thesis Doctorat d’Etat, Faculté des Sciences Semlalia, Univ Cadi Ayyad, Marrakech, Morocco
El Hadrami I (2002) Infections racinaires localisées et rôle des dérivés hydroxycinnamiques dans la résistance du palmier dattier (Phoenix dactylifera L.) au Fusarium oxysporum f. sp. albedinis, agent causal du Bayoud. Polyphen Actual 22:19–27
El Hadrami I, Baaziz M (1995) Somatic embryogenesis and analysis of peroxidases in Phoenix dactylifera L. Biol Plant 37:197–203
El Hadrami I, Coumans M (1994) Somatic embryogenesis in Phoenix dactylifera L: relation with phenolic compounds. In: de Kouchkovsky Y, Larher F (eds) Plant sciences. SFPV-Université de Rennes I, France, p 155
El Hadrami I, El Hadrami A (2009) Breeding date palm. In: Jain SM, Priyadarshan PM (eds) Breeding plantation tree crops. Springer, New York, pp 191–216
El Hadrami I, Cheikh R, Baaziz M (1995) Somatic embryogenesis and plant regeneration from shoot-tip explants in Phoenix dactylifera L. Biol Plant 37:205–211
El Hadrami I, El Bellaj M, El Idrissi A et al (1998) Biotechnologies végétales et amelioration du Palmier dattier (Phoenix dactylifera L.), pivot de l’agriculture oasienne marocaine. Cah Agric 7:463–468
El Hadrami A, El Idrissi-Tourane A, El Hassni M et al (2005) Toxin based in vitro selection and its potential application to date palm for resistance to the bayoud fusarium wilt. A review. C R Biol 328:732–744
El Hadrami I, Daayf F, El Hadrami A (2010) On the socio-economical importance and traditional, health benefits, functional food and nutraceutical uses of dates. In: Manickavasagan A et al (eds) Dates – production, processing, marketing, food and medicine
El Hassni M, El Hadrami A, Daayf F, El Hadrami I (2004a) Chitosan, antifungal product against Fusarium oxysporum f. sp. albedinis and elicitor of defence reactions in date palm roots. Phytopathol Mediterr 43:195–204
El Hassni M, J’Aiti F, Dihazi A et al (2004b) Enhancement of defense responses against Bayoud disease by treatment of date palm seedlings with an hypoaggressive Fusarium oxysporum isolate. J Phytopathol 152:1–8
El Hassni M, El Hadrami A, Daayf F et al (2007) Biological control of Bayoud disease in date palm: selection of microorganisms inhibiting the causal agent and inducing defense reactions. Environ Exp Bot 59:224–234
El Houmaizi MA, Saaidi M, Oihabi A, Cilas C (2002) Phenotypic diversity of date-palm cultivars (Phoenix dactylifera L.) from Morocco. Genet Res Crop Evol 49:483–490
El-Assar AM, Krueger RR, Devanad PS, Chao CT (2005) Genetic analysis of Egyptian date (Phoenix dactylifera L.) accessions using AFLP markers. Genet Res Crop Evol 52:601–607
El-Kharbotly A, El-Mardi M, Al-Saadi N, Al-Mahruki Y (1998) Towards the construction of a genetic map of date palms using the amplified fragment length polymorphism technique (AFLP). In: Proceedings of the first international conference on date palms. Al-Ain, United Arab Emirates, pp 194–207
Ellis MH, Spielmeyer W, Gale KR et al (2002) “Perfect” markers for the Rht-B1b and Rht-D1b dwarfing genes in wheat. Theor Appl Genet 105:1038–1042
El-Sharabasy SF, Wanas WH, Al-Kerdany AY (2008) Effect of salinity stress on some date palm cultivars during proliferation stage in vitro. Arab J Biotechnol 11:273–280
Elshibli S, Korpelainen H (2008) Microsatellite markers reveal high genetic diversity in date palm (Phoenix dactylifera L.) germplasm from Sudan. Genetica 134:251–260
Elshibli S, Korpelainen H (2009a) Excess heterozygosity and scarce genetic differentiation in the populations of Phoenix dactylifera L.: human impact or ecological determinants. Plant Genet Res 7:95–104
Elshibli S, Korpelainen H (2009b) Biodiversity of date palms (Phoenix dactylifera L.) in Sudan: chemical, morphological and DNA polymorphisms of selected cultivars. Plant Genet Res 7:194–203
Fedak G (1999) Molecular aids for integration of alien chromatin through wide crosses. Genome 42:584–591
Fki L, Masmoudi R, Drira N, Rival A (2003) An optimized protocol for plant regeneration from embryogenic suspension cultures of date palm (Phoenix dactylifera L.) cv. Deglet Nour. Plant Cell Rep 21:517–524
Fry JD (2010) The genomic location of sexual antagonistic variation: some cautionary comments. Evolution 64:1510–1516
Gorelick R (2003) Evolution of dioecy and sex chromosomes via methylation driving Muller’s ratchet. Biol J Linn Soc 80:353–368
Gorelick R (2005) Theory for why dioecious plants have equal length sex chromosomes. Am J Bot 92:979–984
Gorelick R, Osborne R (2002) Inducing sex change and organogenesis from tissue culture in the endangered African cycad Encephalartos woodii (Cycadales, Zamiaceae). S Afr J Sci 98:114–117
Hela S, Trifi M, Oould Mohamed Salem A et al (2000) Rapid construction of a random genomic library from date palm (Phoenix dactylifera L.). Plant Mol Biol Rep 17:1–7
Ibrahim AMF, El Kobbia AM, Kitat FM, Abd El Kawy MM (1998) Cytological studies on date palm. I. Chromosomal behavior during meiosis of two date palm (Phoenix dactylifera L.) male types. Alex J Agric Res 43:237–246
J’Aiti F, Verdeil JL, El Hadrami I (2009) Effect of jasmonic acid on the induction of polyphenoloxidase and peroxidase activities in relation to date palm resistance against Fusarium oxysporum f. sp. albedinis. Physiol Mol Plant Pathol 74:84–90
Jain SM (2006) Radiation-induced mutations for developing Bayoud disease resistant date palm in North Africa. In: Proceedings of the international workshop on true-to-typeness of date palm tissue culture-derived plants, Morocco, 23–25 May 2005. UAE University, Date Palm Global Network, Al Ain, United Arab Emirates, pp 31–41
Jain SM (2007) Recent advances in plant tissue culture and mutagenesis. Acta Hortic 736:205–211
Jain SM (2009) In vitro culture and mutagenesis in genetic improvement of date palm. In: Proceedings of 4th Date palm conference, Saudi Arabia, 5–8 May 2007 (in press)
Jain SM, Gupta P (eds) (2005) Protocols of somatic embryogenesis in woody plants. Springer, Dordrecht
Loutfi K (1999) Organogenèse et embryogenèse somatique à partir des tissus floraux du palmier dattier (Phoenix dactylifera L.) cultivés in vitro. Aspects histologiques et caryologie des vitroplants. Thesis Doctorat d’Etat, Faculté des Sciences Semlalia, Marrakech, Morocco
Loutfi K, El Hadrami I (2004) Phoenix dactylifera L.: date palm. In: Litz RE (ed) Biotechnology of fruit and nut crops, vol 29. CAB International, Wallingford, pp 144–156
Majourhat K, Bendiab K, Medraoui L, Baaziz M (2002) Diversity of leaf peroxidases in date palm (Phoenix dactylifera L) as revealed in an example of marginal (seedling-derived) palm groves. Sci Hortic 95:31–38
McCallum CM, Comai L, Greene EA, Henikoff S (2000) Targeting induced local lesions in genomes (TILLING) for plant functional genomics. Plant Physiol 123:439–442
McCubbin MJ, Zaid A, van Staden J (2004) A southern African survey conducted for off-types on date palms produced using somatic embryogenesis. Emir J Agric Sci 16:8–14
Munier P (1973) Le palmier dattier. Coll. Techniques Agricoles et Productions Tropicales, XXIV. Maisonneuve and Larose, Paris
Nemec B (1910) Das problem der befruchtungsvorgänge und andere zytologische Fragen. Borntraeger, Berlin
Omer MS, Hameed MK, Al-Rawi MS (1992) Micropropagation of date palm (Phoenix dactylifera L.). In: Bajaj YPS (ed) Biotechnology in agriculture and forestry, vol 18, High-tech and micropropagation II. Springer-Verlag, Berlin, pp 471–490
Ouenzar B (2003) Contribution à l’amélioration du Palmier dattier: recherche de marqueurs moléculaires précoces de la détermination du sexe et de la résistance au Bayoud. Thesis Doctorat d’Etat, Faculté des Sciences Semlalia, Marrakech, Morocco
Ouenzar B, Hartmann C, Rode A et al (2003) Détermination de la taille génomique du palmier dattier par cytométrie en flux. In: El Hadrami I, Daayf F (eds) Biotechnologies végétales: de la structure des génomes à l’amélioration des plantes. El Watanya, Marrakech, pp 70–77
Reuveni O (1979) Embryogenesis and plantlets growth of date palm (P. dactylifera L.) derived from callus tissues. Plant Physiol 63:138 (Abstract)
Reynolds JF, Murshige T (1979) Asexual embryogenesis in callus cultures of palms. In Vitro 15:383–387
Rice WR (1984) Sex-chromosomes and the evolution of sexual dimorphism. Evolution 38:735–742
Saker M, Bekheet S, Taha H et al (2000) Detection of somaclonal variation in tissue culture-derived date palm plants using isozyme analysis and RAPD fingerprints. Biol Plant 43:347–351
Saker MM, Adawy SS, Mohamed AA, El-Itriby HA (2006) Monitoring of cultivar identity in tissue culture-derived date palms using RAPD and AFLP analysis. Biol Plant 50:198–204
Salem AOM, Trifi M, Sakka H, Rhouma A, Marrakchi M (2001) Genetic inheritance analysis of four enzymes in date palm (Phoenix dactylifera L.). Genet Res Crop Evol 48:361–368
Sedra MH, Lashermes P, Trouslot P et al (1998) Identification and genetic diversity analysis of date-palm (Phoenix dactylifera L.) varieties from Morocco using RAPD markers. Euphytica 103:75–82
Seki M, Narusaka M, Abe H et al (2005) Monitoring the expression pattern of 1300 Arabidopsis genes under drought and cold stresses by using a full-length cDNA microarray. Plant Cell 13:61–72
Sghaier B, Bahloul M, Bouzid GR, Drira N (2008) Development of zygotic and somatic embryos of Phoenix dactylifera L. cv. Deglet Nour: comparative study. Sci Hortic 116:169–175
Sghaier-Hammami B, Drira N, Jorrín-Novo JV (2009) Comparative 2-DE proteomic analysis of date palm (Phoenix dactylifera L.) somatic and zygotic embryos. J Proteomics 73:161–177
Siljak-Yakovlev S, Benmalek S, Cerbah M et al (1996) Chromosomal sex determination and heterochromatin structure in date palm. Sex Plant Reprod 9:127–132
Snoussi H, Du Jardin P, Ben Abdallah A, Lepoivre P (2001) Assessment of genetic variation within date palm (Phoenix dactylifera L.) using amplified fragment length polymorphism (AFLP) – genotyping of apomictic seedlings as a case study. In: Proceedings second international conference on date palms. Al-Ain, UAE, 25–27 Mar 2001, pp 678–683. URL: http://www.pubhort.org/datepalm/index2.htm
Soliman SS, Ali BA, Ahmed MMM (2003) Genetic comparisons of Egyptian date palm cultivars (Phoenix dactylifera L.) by RAPD-PCR. Afr J Biotechnol 2:86–87
FAO Statistics (2010) www.fao.org
Sudhersan C, Abo El-Nil M, Al-Baiz A (1993) Occurrence of direct somatic embryogenesis on the sword leaf of in vitro plantlets of Phoenix dactylifera L. cultivar Barhee. Curr Sci 65:887–888
Sudhersan C, Al-Shayji Y, Jibi Manuel S (2009) Date palm crop improvement via TxD hybridization integrated with in vitro culture technique. Acta Hortic 829:219–224
Swingle WT (1928) Metaxenia in the date palm. J Hered 19:257–268
Talaat AA, Al-Qaradawi A (2009) Molecular phylogeny of Qatari date palm genotypes using simple sequence repeats markers. Biotechnology 8:126–131
Tanksley SD (1993) Mapping polygenes. Annu Rev Genet 27:205–233
Tisserat B (1979) Propagation of date palm (Phoenix dactylifera L.) in vitro. J Exp Bot 30:1275–1283
Tisserat B (1984) Propagation of date palms by shoot tip cultures. Hort Sci 19:230–231
Toutain G, Louvet J (1972) Resistance to Bayoud in varieties of date palm. In: First international seminar and workshop on bayoud, Oct 1972, ITAS, Alger, pp 208–210
Trifi M, Rhouma A, Marrakchi M (2000) Phylogenetic relationships in Tunisian date- palms (Phoenix dactylifera L.) germplasm collection using DNA amplification fingerprinting. Agronomie 20:665–671
Veramendi J, Navarro L (1996) Influence of physical conditions of nutrient medium and sucrose on somatic embryogenesis of date palm (Phoenix dactylifera L.). Plant Cell Tissue Org Cult 45:159–164
Wong CK, Bernardo R (2008) Genomewide selection in oil palm: increasing selection gain per unit time and cost with small populations. Theor Appl Genet 116:815–826
Wrigley G (1995) Date palm (Phoenix dactylifera L.). In: Smartt J, Simmonds NW (eds) The evolution of crop plants. Longman, London, pp 399–403
Zaid A (2002) Date palm cultivation. Plant Production and Protection Paper 156. FAO, Rome
Zehdi S, Trifi M, Salem AOM (2002) Survey of inter simple sequence repeat polymorphisms in Tunisian date palms (Phoenix dactylifera L.). J Genet Breed 56:77–83
Zehdi S, Sakka H, Rhouma A et al (2004a) Analysis of Tunisian date palm germplasm using simple sequence repeat primers. Afr J Biotechnol 3:215–219
Zehdi S, Trifi M, Billotte N et al (2004b) Genetic diversity of Tunisian date palms (Phoenix dactylifera L.) revealed by nuclear microsatellite polymorphism. Hereditas 141:278–287
Zivdar S, Mousawi M, Alemzadeh Ansari N (2008) Genetic stability in date palm micropropagation. Asian J Plant Sci 7:775–778
Zohary D, Spiegel-Roy P (1975) Beginnings of fruit growing in the old world. Science 187:319–327
Zouine J, El Hadrami I (2007) Effect of 2,4-D, glutamine and BAP on embryogenic suspension culture of date palm (Phoenix dactylifera L.). Sci Hortic 112:221–226
Zouine J, El Bellaj M, Meddich A et al (2005) Proliferation and germination of somatic embryos from embryogenic suspension cultures in Phoenix dactylifera L. Plant Cell Tissue Org Cult 82:83–92
Acknowledgments
This review has been supported by equal contribution from several research grants to Professor I. El Hadrami (IFS/AUF/PRAD/CNRST/AI Morocco-Tunisia/AI Morocco-France). The authors would like to thank Drs S. M. Jain and J. M. Al-Khayri for their critical review of the first draft of this contribution.
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Hadrami, A.E., Daayf, F., Hadrami, I.E. (2011). Date Palm Genetics and Breeding. In: Jain, S., Al-Khayri, J., Johnson, D. (eds) Date Palm Biotechnology. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-1318-5_23
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