Perilla is an oil and vegetable crop growing in Korea, Japan, and China. We have conducted a field expedition for collecting Perilla germplasm in Korea in 1998 and 2002. P. frutescens var. frutescens was found to be grown and cultivated in large scale throughout the country, whereas var. crispa was not seen. Weedy types of both var. frutescens and var. crispa were often found in roadsides, waste lands and areas around the farmer’s fields. Total number of collection was 176 with 123 accessions of cultivated type of var. frutescens, 33 accessions of weedy type of var. frutescens, and 20 accessions of weedy type of var. crispa. The accessions of cultivated var. frutescens had four different seed coat colors; white, gray, brown and dark brown. Brown and dark brown types were more frequently found than the white type and distributed from north to south of Korea, whereas the white type was mainly found in southern part of Korea. The seeds of cultivated var. frutescens were either soft or hard and large in size (> 2mm), whereas seeds of both weedy types were small and hard with dark brown color. The accessions collected will be useful for preserving genetic diversity of this crop for further breeding programs of Perilla crops.

We investigated the variations of the flowering response to daylength in Perilla crop (var. frutescens). Seventeen accessions of Perilla crop and one accession of weedy type of var. crispa from China, Korea and Japan were cultivated under three daylength conditions, i.e., short-days, natural daylength and long-days. Most accessions of Perilla crop from China, Korea and Japan were divided into three types, early maturing type, intermediate maturing type and late maturing type by their natural flowering habit. In most of the accessions used, the flowering habit was significantly accelerated by short-day conditions and was delayed by long-day conditions. All the accessions of Perilla crops flowered within 57 days under the 10 hrs light treatment, whereas they did not flower at all even at 170 days after sowing under the 16 hrs light treatment. Thus, this finding suggested that there is a relationship between the types of flowering response to daylength and the geographical distribution which determines the planting season in traditional cultivation practices of Perilla crops. Positive correlation was observed between days to flowering and plant height or internode number in both the short-day and natural daylength conditions. Whereas, correlation was negative between days to flowering and inflorescence length or floret number in natural daylength condition, but it was positive in the short-day condition. Therefore, the daylength condition is considered as the most important environmental factor for flowering habit and morphological characters of Perilla crops. Flowering habit is considered as an important key character for the study of geographical differentiation of Perilla crop in East Asia.