Maternal origin diversity of nine olive varieties bred in China

[Objective] The study aims to compare the genetic diversity and relationship between chloroplast genomes of olive varieties bred in China and those in the mediterranean olives, and to estimate the maternal diversity of olive varieties bred in China, in order to provide a basis for the development of Chinese olive accessions. [Methods] NOVOPlasty v.4.3.1 was used to assemble chloroplast genomes, which were based on the genome re-sequencing data of nine olive varieties bred in China and seven Iranian accessions, both of which were sequenced in this study, as well as fifty-two mediterranean olive accessions downloaded from the database. The sequence polymorphism was calculated. GPA, RAxML-NG, and Network 5.0, and other softwares were used to construct the chloroplast genome map, the relationship of phylogeny, and the network of haplotype, respectively. [Results] The chloroplast genomes of the tested olive accessions were consistent in terms of tetrad structure and number of genes. All chloroplast genomes identified seventeen haplotypes, among which the olive varieties bred in China had only one haplotype which was shared with the most mediterranean cultivated olives. The oleasters had the highest genetic diversity, followed by the mediterranean cultivated olives and then Iranian accessions, while nine olive varieties bred held all genetic diversity of 0. The phylogenetic relationship was consistent with the network of haplotype, and one branch contained most of the mediterranean cultivated varieties, including the Iranian olive accessions and all olive varieties bred in China. [Conclusion] The nine olive varieties bred in China shows an extremely low diversity of maternal origin. It is necessary to select and breed the olive varieties adapted to the habitats in China from a more comprehensive lineage of olive accessions in the later stages.