Clonal propagation and molecular analysis of date palm (Phoenix dactylifera L.)

Abstract

Somatic embryogenesis is the mass production system of choice for date palm to increase the rates of vegetative propagation. However, the low rates of conversion to plants are common for somatic embryos. Up to 50% of plant productiqn in the Jimmah Tissue Culture Laboratory, Oman is lost during the stages of somatic embryo germination and conversion. Partial desiccation of date palm somatic embryos of the genotype Khalas Aldahra, either by dehydration for up to 4 hours or supplementation of the maturation Murashige and Skoog-based medium with sorbitol, sucrose and polyethylene glycol, increased significantly the percentage conversion to plants. In contrast, the addition of indol-3-butyric acid (IBA), a-naphthaleneacetic acid (NAA), 6-benzylaminopurine (BAP), abscisic acid (ABA), flurprimidol or activated charcoal to the germination medium did not improve the conversion of embryos to plants compared to the control. A protocol for cryopreservation of somatic embryos and embryogenic cultures of the genotype Buhabisha was developed in the current study using the vitrification method (incorporating PVS2 solution) and pretreatment with glycerol, sorbitol and dimethylsulfoxide as a cryoprotectant prior to freezing. Despite the fact that, there was a low percentage of survival of somatic embryos, the results from this study provided evidence that it is possible to cryopreserve somatic embryos and embryogenic callus of Omani date palms. A cell suspension protocol from the genotype Buhabisha was established in this study in order to utlilise more efficient micropropagation methods and to overcome the problems of the large size of somatic embryos that may lead to an efficient cryopreservation technique. NAA gave the best regeneration frequency of somatic embryos compared to 2,4-dichlorophenoxyacetic acid (2,4-D) or picloram. However, attempts to replace activated charcoal in the date palm cultures with either polyvinylpyrolidone or ascorbic acid were unsuccessful. The use of dialysis membrane to separate cell suspensions from activated charcoal was successful, but the generation of somatic embryos was low. Twenty one genotypes obtained from the Jimmah Research Station, Oman were screened and evaluated with microsatelIite markers to establish a DNA fingerprinting procedure. Simple Sequence Repeats (microsatellites) showed that date palm genotypes analysed had high genetic divergence. Importantly, somaclonal variation was not detected by DNA fingerprinting in tissue culture-derived plants of the genotype Khalas Aldahra.EThOS - Electronic Theses Online ServiceGBUnited Kingdo