Ecological Impacts of Sunflowers on Soil Microbial Communities: Insights from Full-Length 16S rRNA Sequencing

Sunflower (Helianthus annuus L.), a widely cultivated oilseed crop, is occasionally found growing in non-cultivated areas in South Korea, raising concerns about its unintentional potential ecological impacts. This study investigated the effects of two naturalized sunflower cultivars with varying seed dispersal densities on soil microbial communities in a simulated natural ecosystem. A field experiment was performed using 2 × 2 m plots designed to simulate natural ecosystems. The crops incorporated two types of sunflowers with different seed densities. Microbiome samples were collected at the pre-sowing, growing, and flowering stages and subsequently analyzed using the PacBio Sequel platform. Using long-read sequencing of full-length 16S rRNA genes via the PacBio Sequel II platform, we identified 9,885 amplicon sequence variants (ASVs), including key indicator species significantly correlated with seed density. While sunflowers demonstrated limited dominance and no significant alterations to overall community structure, specific microbial taxa, such as Phycicoccus ginsenosidimutans and Flavisolibacter ginsengiterrae, were strongly associated with sunflower growth. These findings provide critical insights into the potential ecological impacts of sunflower introductions and underscore the importance of full-length 16S rRNA sequencing for accurate microbial identification. This study highlights the need for continuous monitoring and contributes to advancing risk assessment methodologies for naturalized plants in natural ecosystems.