Morphological Variation Among Commercial Cultivars and Weed-Like Accessions of Perilla frutescens Collected in South Korea and Japan

This study evaluated morphological variation in 45 accessions of cultivated Perilla frutescens var. frutescens (PFF) and var. crispa (PFC) collected from South Korea and Japan, together with their weedy counterparts, var. frutescens (WPFF) and var. crispa (WPFC) from South Korea, using ten quantitative and ten qualitative traits. Clear morphological differentiation was observed between cultivated and weedy forms in both varieties, particularly in pigmentation, plant fragrance, and seed-related traits. PFF cultivars were characterized by predominantly green pigmentation, a typical frutescens aroma, and significantly larger and heavier seeds, suggesting stronger phenotypic differentiation in leaf and seed utilization. In contrast, PFC cultivars showed substantial morphological overlap with WPFC and WPFF accessions, indicating comparatively weaker phenotypic differentiation. Principal component analysis showed that the first principal component (PC1) explained 25.7% of the total phenotypic variance and was strongly associated with five quantitative traits (plant height, inflorescence length, floret number, seed size, and 100-seed weight) and five qualitative traits (adaxial and abaxial leaf color, flower color, seed color, and seed hardness). Along PC1, PFF cultivars formed a well-defined cluster, whereas PFC cultivars and the weedy WPFF and WPFC accessions exhibited broader dispersion, reflecting greater morphological variability. These results provide morphological insights into the differentiation between cultivated and weedy Perilla accessions and indicate potential domestication-related patterns. However, these interpretations are based primarily on morphological observations, and further genetic and evolutionary studies will be necessary to clarify the domestication history of these taxa. The identified trait complexes provide a useful phenotypic foundation for marker-assisted breeding, informed cultivar selection, and effective germplasm conservation and management.