Selection and multiplication of an elite genotype of Ziziphus spinachristi from seedling populations in Kuwait

Different species of Ziziphus such as Z. spinachristi, Z. mauritiana, Z. xylopyrus and Z. jujuba were introduced in Kuwait due to its ability in tolerating the harsh arid environmental climatic conditions. Due to the pollen compatibility between different species of Ziziphus, several superior genotypes were noticed in the seedling populations. Recently, a project study was carried out in the Kuwait Institute for Scientific Research (KISR) on genotype selection from seedling populations of Z. spinachristi for the nutritive fruits. Seeds were collected from the locally grown Z. spinachristi and 5,000 seedlings were produced. Among the 5,000 seedlings, 500 plants were planted in the field. After one year of planting, all the plants started producing flowers and fruits. Most of the plants were varied in their fruit quality (size, shape and taste). A stone-less superior genotype was identified during the field evaluation. The selected genotype has produced sweet stone-less large fruits with attractive color. The fruits have fertile seeds without a hard stone around. Two viable seeds without stone were observed in each fruit until the fruit bigan ripening and the seeds aborted during the ripening stage due to the lack of stone around the seeds. Tissue culture technology was applied for the mass clonal propagation of this elite genotype. A technique for rapid in vitro multiplication, rooting and establishment of plantlets in the field was developed and described. The influence of growth regulators in the regeneration, growth and multiplication medium on plantlet growth and rooting was assessed. Rapid propagation was achieved by the zygotic embryo rescue, axillary shoot multiplication and somatic embryogenesis methods. Plants were established successfully in the greenhouse through the maintenance of a high humidity environment for 30 days and hardened plantlets were subsequently transferred to the field. Field evaluation of these micropropagated plants confirmed the clonal nature through producing true-to-type fruits similar to the mother.