Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 7/1/2014
Publication Date: 1/1/2015
Citation: Jaradat, A.A. 2015. Biodiversity, genetic diversity and genetic resources of date palm. In: Al-Khayri, J.M., Jain, S.M. and Johnson, D.V., editors. Date Palm Genetic Resources and Utilization. New York, NY: Springer. p. 19-71.
Interpretive Summary: Man-made selection and vegetative propagation of date palms in the oases greatly altered their original genetic structure. The date palm is the dominant component upon which the oasis agro-ecosystem is based. The tremendous advantage of the date palm tree is its resilience, its long-term productivity, and its multipurpose attributes. However, some of its unique characteristics have severely restricted its improvement using traditional breeding methods. Although the date palm may not be immediately threatened by natural or man-made factors, several reports indicated that the level of genetic diversity as to the number of cultivars in oases is declining due to several factors. This introductory chapter provides detailed information on wild and domesticated date palm, how and where it was domesticated from the wild, tree and fruit traits that changed upon domestication, and an assessment of the factors affecting its variation, especially in view of climate change. An assessment is provided of date palm genetic resources that can be used to improve its resilience under disease, insect and climate stresses. Also, research needs and priorities are outlined to inform students about the biodiversity and genetic diversity of this unique fruit tree, and to provide guidelines for farmers and scientists working with date palm to plan for its proper conservation in traditional oases and new commercial plantations under a changing climate.
Technical Abstract: Phoenix dactylifera is composed of genetically discrete clones representing thousands of cultivars without the benefits of a dynamic mutation-recombination system; its genetic resources are the most important component of biodiversity in its natural habitats; these include modern cultivars, landraces, obsolete cultivars, breeding lines, and related wild species. Cultivated Phoenix is closely related to a variable aggregate of wild and feral palms distributed over a wide desert belt across the Middle East and North Africa. Genetic diversity and genetic structure of the species gene pool complex have been shaped and greatly altered by human and natural selection, clonal propagation, and spatio-temporal exchange of germplasm. The mixed sexual-clonal propagation system acted on the sexual traits, impacted the genetic structure of populations, and may have resulted in the accumulation of domesticated traits in the date palm. Traditional oases continue to play a vital role in the maintenance and enrichment of date palm biodiversity, genetic diversity and genetic resources through multiple processes and dynamic conservation practices. However, with the advent of modern plantations emphasizing elite cultivars, a better understanding of the intra-specific genetic variation of date palm and its distribution in oasis agro-ecosystems is essential for the conservation and sustainable utilization of its biodiversity and genetic resources. In-depth assessment of the genetic vulnerability of date palm to biotic and abiotic stress requires knowledge of the extent and distribution of its genetic diversity, both of which depend on the species evolution and its unique breeding system, past genetic bottlenecks, and ecological, environmental and anthropogenic factors.