Construction of a core germplasm collection of Fraxinus mandshurica based on phenotypic traits and genome-wide simple sequence repeat (SSR) markers

Key message

Fraxinus mandshurica genetic diversity is assessed using phenotypic and SSR markers, leading to the establishment of a core germplasm collection and offering insights for future breeding and conservation.

Abstract

Fraxinus mandshurica is a principal tree for afforestation and timber production, providing considerable ecological and economic value. To assess Fraxinus mandshurica clonal genetic diversity, 217 germplasm samples were collected from Heilongjiang, Jilin, and Liaoning provinces. First, the coefficient variation for the 11 phenotypic traits ranged from 16.44% to 54.92%. A 15% sampling ratio was applied to select core germplasm, resulting in 34 samples with no significant trait differences from the original collection. Furthermore, a total of 95,437 SSR loci were identified based on the whole genome, with an average distance of 8.174 kilobases per locus. Seven pairs of highly polymorphic SSR primers were selected, with an average polymorphism information content of 98.58%. Subsequently, genetic analysis of 217 clones using four SSR primer pairs identified 86 loci, classified into three subgroups, and established a core germplasm collection of 43 samples. Finally, a primary core germplasm bank of 66 clones was established by combining both phenotypic and SSR molecular markers. Genetic analysis indicated a negative genetic gain for Na, while PIC showed a significant improvement of 10.55%. Phenotypic analysis showed notable increases in the length-to-width ratio of the second-order compound leaves and the ground diameter, with improvements of 2.01% and 1.72%, respectively. Overall, the core germplasm collection effectively represents the genetic diversity of the original collection. This study provides theoretical references for further investigating genetic diversity, laying the foundation for future research on the genetic evaluation and utilization of Fraxinus mandshurica germplasm.