Lack of evidence of culturable Phytophthora in naturally regenerated European beech seedlings and seeds

Soilborne oomycetes of the genus Phytophthora are an increasing concern in European beech ( Fagus sylvatica ) forests, where they can damage root systems and contribute to tree decline. Because Phytophthora inoculum may persist in soil and is difficult to eradicate once established, naturally regenerated seedlings in affected stands may be exposed to infection during early development. At the same time, natural regeneration may reduce some biosecurity risks associated with planting nursery stock, a recognized pathway for Phytophthora spread. However, although Phytophthora has been extensively studied in mature beech stands and forest nurseries, little is known about whether naturally regenerated beech seedlings become infected during the earliest stages of establishment in previously infested forests. We addressed this question by examining culturable fungi and oomycetes associated with naturally regenerated beech seedlings and beech seeds collected from a protected beech forest in southern Sweden with previous records of Phytophthora . Seedling condition was assessed using root and foliar symptoms, and isolates that were cultured in selective media from seedling roots and seeds were identified using ITS rDNA sequencing. Root lesions were common, but no culturable Phytophthora were recovered from either seedling roots or seeds. Instead, seedling roots yielded 361 isolates dominated by common soil- and root-associated fungi, including Clonostachys sp., Metapochonia bulbillosa , and Aspergillus sp., indicating that diverse culturable fungi were present despite the non-recovery of Phytophthora . Seeds yielded 73 isolates, with 34 ITS sequences representing 11 taxa, mainly Linnemannia , Fusarium , and Clonostachys taxa. Further studies using molecular methods are needed to clarify whether Phytophthora persists at low levels or if other soil fungi are more persistent during early regeneration stages.