Genetic diversity, population structure, and DNA fingerprinting of Ailanthus altissima var. erythrocarpa based on EST-SSR markers

Ailanthus altissima var. erythrocarpa is an A. altissima variety with high economic, ecological and ornamental value, but there have been no reports on the development of SSR primers for it. According to the SSR primer information provided by the transcriptome of A. altissima var. erythrocarpa, 120 individuals with different redness levels were used to screen polymorphic primers. Transcriptomic analysis revealed 10,681 SSR loci, of which mononucleotide repeats were dominant (58.3%), followed by dinucleotide and trinucleotide repeats (16.6%, 15.1%) and pentanucleotide repeats (0.2%). Among 140 pairs of randomly selected primers, nineteen pairs of core primers with high polymorphism were obtained. The average number of alleles (Na), average number of effective alleles (Ne), average Shannon's diversity index (I), average observed heterozygosity (Ho), average expected heterozygosity (He), fixation index (F) and polymorphic information content (PIC) were 11.623, 4.098, 1.626, 0.516, 0.696, 0.232 and 0.671, respectively. Nineteen EST-SSR markers were used to study the genetic diversity and population structure of A. altissima var. erythrocarpa. The phylogenetic tree, PCoA, and structure analysis all divided the tested resources into two categories, clearly showing the genetic variation between individuals. The population showed high genetic diversity, mainly derived from intraspecific variation. Among nineteen pairs of primers, 4 pairs (p33, p15, p46, p92) could effectively distinguish and be used for fingerprinting of the tested materials. This study is of great significance for genetic diversity analysis and molecular-assisted breeding of A. altissima var. erythrocarpa.