Growth patterns of curly birch seedlings produced through open pollination and identification of the individuals carrying the ‘figured grain’ trait using BpCW1 molecular marker

The article reports the results of research on the growth of one-year-old curly birch seedlings produced through open pollination and growing in the Leningrad Region in the Gatchina permanent seed production stand (PSPS), training nursery of the Lisino Forest College (Shapki plantation), and arboretum of the St. Petersburg Forestry Research Institute (StPFRI). It is demonstrated that the seedlings’ parameters varied significantly depending on the seed collection year and method. Thus, the average height of seedlings in the StPFRI arboretum by the fall 2023 was 51.4 cm and their root collar diameter was 1.6 mm. In 2024, the average values of these parameters were the highest in seedlings grown from seeds collected in the Gatchina PSPS (20.5 cm and 2.5 mm, respectively) and the lowest in seedlings originating from the StPFRI arboretum (8.2 cm and 1.6 mm). Application of the BpCW1 molecular marker permitted detecting the seedlings with the ‘figured grain’ trait as early as in their first year, whereas this trait would normally have exterior manifestations only at 8 years of age or even later. PCR analysis revealed homo- or heterozygous (476 base pairs or 476/530 base pairs) amplification products characteristic of figured-grain curly birch plants in 43% of the analyzed seedlings, which is notably higher than accepted previously for seed progeny from open pollination. Our analysis of the growth parameters shows that the ‘non-figured’ plants had approximately 1.5-fold higher average height and diameter than the ‘figured’ plants irrespective of the seed provenance. However, these parameters are insufficient for differentiating between ‘figured’ and ‘non-figured’ plants considering the life-form polymorphism of curly birch. It is concluded that seeds from open pollination can be used to produce curly birch planting stock provided that the ‘figured grain’ trait is identified in them by the BpCW1 molecular marker, which is nearly unidentifiable at an early age using conventional methods based on the analysis of exterior (morphological) traits.

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