Maturity Grouping of Korean Soybean Cultivars and Character Relationships According to the Planting Date

This study was carried out to classify Korean soybean varieties base on maturity group (MG) and to find character relationships according to planting date for high quality soybean seed production adapted to early season cultivation environment of Miryang. Results of maturity grouping of Korean soybean varieties showed that Keunol (3 cultivars), belonged to Group 0; Seonnok and Danmi in Group II, Shinrok in Group III, Seonyu (17 cultivars), in Group IV, Taekwang (44 cultivars) in Group V, Daewon (25 cultivars) in Group VI, and Kwangdu and Keumdu in Group VII. Agronomic characteristics of 100 soybean varieties were compared based on MG, cultivation year and seeding date. Soybean varieties belonging to the MG VI~VII showed longer days to flowering and growth period, high lodging density and higher yield. Seed quality analysis revealed that as maturity was delayed, seed weight becomes heavier while seed cracks become abundant. In addition, occur-rence of purple seed and phomopsis were higher in MG 0~III. Protein content was higher in MG 0~III, and iso-flavone content was higher as maturity was delayed. On the other hand, lipid content was generally similar across MGs. Correlation analysis of major agronomic characters showed positive relationships between days to flowering and growth days, seed weight and lodging in MG IV~V, seed crack and growth days in MG 0~III, seed crack and days to flowering in MG IV~V and MG VI~VII, seed crack and lodging in MG IV~V and MG VI~VII, seed crack and seed weight in MG IV~V and MG VI~VII, purple seed and growth days in MG IV~V, purple seed and seed weight in MG VI~VII, phomopsis and growth days in MG IV~V and MG VI~VII, and phomopsis and purple seed in MG IV~V and MG VI~VII . In contrast, a negative relationship was observed between seed weight and lodging in MG 0~III. Correlating yield and major characters revealed negative relationships between days to flowering and growth days in MG 0~III and MG IV~V, whereas positive relationships were obtained on MG VI~VII seeded on April 30. Lodging, seed weight and seed crack were all negatively correlated with yield in the MG IV~V and MG VI~VII. Soybean cultivars identified as adaptable to early season planting for production of high quality soy curd and fermented soybean paste were Seonyu, Kwangdu, and Soho while those suited for the manufacture of soybean sprouts were Sobaeknanul, Kwangan, Sowon, and Bosuk. Geomjeong 2 chosen as best for mixing with rice.