2018 ASHS Annual Conference

Simple sequence repeats (SSRs) in chloroplast genomes are useful markers to determine maternal lineages. The SSR mining results revealed that most chloroplast SSRs among three Prunus chloroplast genomes were conserved in locations and motif types, but polymorphic in motif and/or amplicon lengths. Fifty seven of the 67 shared SSRs were polymorphic between at least two of the three chloroplast genomes. Eight SSRs with most in silico polymorphisms were selected to genotype a large collection of peach (P. persica) genotypes and determine their maternal lineages. The genotyping data distinguished these peach genotypes into eight unique maternal lineage groups (MLGs). MLG-1 included most peach cultivars. They apparently belonged to Chinese peach lineage because Chinese Cling in this group was heavily used in early peach development in the US. MLG-2 was the next largest group that presumably belonged to European peach lineage. MLG-3 consisted of only a few ornamental accessions. MLG-4 to 6 included genotypes derived from three wild peach species respectively. MLG-7 and 8 contained only ‘Flordaking’ and ‘Reliance’, respectively. The SSR amplicons from eight representative genotypes, one for each MLG, were sequenced, revealing additional single nucleotide polymorphisms (SNPs) within the amplicon sequences and presumably dividing each MLG into subgroups based on these SNPs. Identification of the maternal lineages may be somewhat helpful for optimal combination of crossing parents. The polymorphisms of these chloroplast SSRs have been validated and may be useful in other phylogenetic studies.