Yield and yield components of a new soybean cultivar, ‘Soratakaku’, in the Chugoku region of Japan

Soybean production in the Chugoku region is often limited by environmental stresses, including excessive soil moisture at sowing and typhoon-induced lodging. To improve productivity under these conditions, new cultivars have been developed. ‘Soratakaku’, a recently developed cultivar derived from Japanese and U.S. cultivar, is expected to exhibit high yield potential in southwestern Japan. The objective of this study was to evaluate the yield performance of ‘Soratakaku’ under both normal and late sowing conditions in the Chugoku region and to identify the morphological and agronomic traits associated with its yield performance. To achieve this objective, ‘Soratakaku’ was cultivated alongside ‘Sachiyutaka A1 gou’ under normal sowing conditions and ‘Fukuyutaka’ under late sowing conditions, and performance was evaluated under different planting densities. Under late-June sowing, ‘Soratakaku’ produced higher yields and dry matter production than ‘Sachiyutaka A1 gou’ under normal and high-density planting despite its lower 100-seed weight. This yield advantage was associated with a greater number of nodes and pods per plant. Under late-July sowing, the yield of ‘Soratakaku’ was comparable to that of ‘Fukuyutaka’ regardless of planting density. Furthermore, the lodging angle of ‘Soratakaku’ was comparable to that of ‘Sachiyutaka A1 gou’ and smaller than that of ‘Fukuyutaka’. Although ‘Soratakaku’ has a maturity similar to that of ‘Fukuyutaka’ and a longer main stem, it exhibited less lodging than the major cultivars. These results suggest that ‘Soratakaku’ achieved higher dry matter production and superior lodging resistance than the major cultivars, and the combination of these traits contributed to its high yield.