Phoenix phylogency, genetic diversity, distribution and population structure characterized in a world collection of date palm (Phoenix dactylifera) and its wild relatives

Authors: CHALUDAVI, S - University Of Georgia; YOUNG, P - University Of Georgia; THOMPSON, K - University Of Georgia; BARHI, B - University Of Georgia; GAJERA, B - Anand Agricultural University; NARYANAN, S - Anand Agricultural University; Krueger, Robert; BENNETZEN, J - University Of Georgia

Submitted to: Plant Diversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2018
Publication Date: 12/18/2018
Citation: Chaludavi, S.R., Young, P., Thompson, K., Barhi, B.A., Gajera, B., Naryanan, S., Krueger, R., Bennetzen, J.L. 2018. Phoenix phylogency, genetic diversity, distribution and population structure characterized in a world collection of date palm (Phoenix dactylifera) and its wild relatives. Plant Diversity. https://doi.org/10.1016/j.pld.2018.11.005.
DOI: https://doi.org/10.1016/j.pld.2018.11.005

Interpretive Summary: Date palm (Phoenix dactylifera) is grown widely in areas with suitable environmental conditions. In this study, it was demonstrated that cultivated date palms are closely allied with wild relatives P. sylvestris, P. pusilla, P. acaulis, and P. caespitosa. The last is native to the Arabian Peninsula and the first three are native to the Indian subcontinent. Microsatellite markers were used to evaluate the genetic diversity in 195 date palm accessions from 13 countries. Extensive genetic diversity was observed. The date palm accessions could be divided into two groups, one with predominantly North African accessions and the other with predominantly Asian accessions, although there were some deviations from this generalization. Overall, there was greater diversity in the Asian accessions than in the African accessions. Many admixed accessions were found, suggesting that the predominant gene flow was from east to west. However, accessions from the Indian subcontinent were more closely related to North African accessions.

Technical Abstract: Date palm (Phoenix dactylifera) is one of the most ancient crops, and is grown commercially in >30 countries. Using whole plastome assemblies, phylogenetic analyses revealed that cultivated date palm accessions share the same clade with P. sylvestris, P. pusilla and P. acaulis, which are native to the Indian subcontinent, and P. caespitosa that is native to the Arabian Peninsula and the deserts of Somalia. Analysis of genetic diversity and genetic relationships among date palm accessions from 13 producing countries involved 195 date palm accessions that were genotyped at 19 microsatellite loci. Extensive genetic diversity was observed, with many accessions heterozygous for most markers in this clonally propagated crop. The average number of alleles per locus (42.1), expected heterozygosity (0.8), observed heterozygosity (0.47) and fixation indices (Fst=0.46) demonstrated significant population structure. Iraqi accessions were found to have the richest allelic diversity, and the most private alleles. Accessions with the same names from different locations usually, but not always, exhibited highly similar SSR profiles. The model-based Bayesian method, STRUCTURE 2.4.1, indicated that these accessions could be broadly divided into two groups, one group with predominantly African accessions and another predominantly Asian. Some germplasm, especially from Tunisia, deviated from this generalization. Overall, greater diversity was found in the Asian accessions than in the African accessions. Many accessions in the STRUCTURE-derived populations were found to be genetic admixtures, suggesting that gene-flow between Asian and African subpopulations has occurred predominantly from east to west, but with the interesting exception that Indian and Pakistani date palms were found to be most closely related to North African germplasm.