The sticky fruit of the date palm has a tangled history. New research in G3 explores the palm’s genetic diversity and traces its earliest cultivation to at least two distinct regions in North Africa and the Arabian Gulf.
The date palm (Phoenix dactylifera) is one of the world’s oldest cultivated trees and has close ties to the history of human civilization and migration. Archaeological evidence suggests people in the middle East were cultivating dates as early as 5000 years ago, but few firm conclusions have been made about the palm’s geographic origin and domestication. With the recent completion of the Phoenix dactylifera genome sequence, genetics can help fill in these gaps. Additionally, delving into the date palm genome can give insight into the tree’s cultivation and can help researchers understand which genes were selected for during its domestication. The selective pressure exerted during domestication of wild plants remains an interesting and poorly understood process.
In the July issue of G3, Mathew et al. use genotyping-by-sequencing (GBS) to analyze over 70 Phoenix dactylifera leaf and fruit samples originating from 10 different countries, as well as samples from four other Phoenix species. Using genome-wide single nucleotide polymorphism (SNP) data, the researchers constructed a date palm phylogenetic tree that split the samples into two major subpopulations. These findings point to two sites of early cultivation, North Africa and the Arabian Gulf, consistent with recent archaeological evidence and emerging theories.
Close to 40% of the SNPs surveyed were “private” to one subpopulation or the other, meaning they were only found in one of the subpopulations. The researchers point out that the high level of genetic separation between the two subpopulations is intriguing considering the political history of the area; despite heavy trade and travel in the region, the two subpopulations remained quite distinct.
CITATION: Mathew LS, Seidel MA, George B, Mathew S, Spannagl M, Haberer G, Torres MF, Al-Dous EK, Al-Azwani EK, Diboun I, Krueger RR, Mayer KF, Mohamoud YA, Suhre K, Malek JA. (2015) A Genome-Wide Survey of Date Palm Cultivars Supports Two Major Subpopulations in Phoenix dactylifera. G3, 5(7):1429-38. doi: 10.1534/g3.115.018341 http://www.g3journal.org/content/5/7/1429.full