Genetic Diversity of the Camellia oleifera Abel. Germplasm and Development of a Core Collection Using Simple Sequence Repeat Markers

Abstract Camellia oleifera is an important oilseed crop. With the increasing attention given to C. oleifera, germplasms have been collected, and banks have recently been established or renewed. The lack of knowledge of genomic SSRs, limited investigation into the genetic diversity of the germplasm bank, and lack of a core collection have hindered the breeding of oil tea. Therefore, genomic libraries were constructed and sequenced, and all clean reads were assembled into 673,863 unigenes. In total, 27,953 SSRs were detected from all the unigenes, and 17,517 SSR primer pairs were successfully designed. Furthermore, we re-evaluated the genetic diversity of the germplasm bank of C. oleifera using 22 SSR markers. The number of alleles (Na) ranged from 4 to 25, with an average of 11.41; the effective number of alleles (Ne) ranged from 2.014 to 9.284, with an average of 4.800; the Shannon index (I) ranged from 0.716 to 2.471, with an average of 1.682; and the polymorphic information index (PIC) ranged from 0.380 to 0.883, with an average of 0.717. Finally, a core collection consisting of 45 samples (15% of the 300 trees in the entire germplasm bank) was developed, the genetic diversity parameters of which showed nonsignificant differences from the entire germplasm bank. Genomic SSR development, the re-evaluation of genetic diversity and the development of a core collection from the germplasm bank in this study provided useful tools, abundant genetic resources and an effective collection for the utilization and deep exploration of C. oleifera.