Development of speed-breeding system for Korean soybean varieties [Glycine max (L.) Merr] using LED light source

Abstract

The conventional soybean breeding program by single seed descent method required around 8 to 9 years to develop a cultivar. Through the advancement of breeding techniques, such as marker-assisted selection, required resources could be significantly saved, but the generation advancement step still slows down the entire soybean breeding program time course. In this study, 28 soybean varieties were tested to find the optimal speed breeding conditions for soybeans that could rapidly advance one generation with 2 light sources, 3 light conditions, and 2 planting densities. Plants were kept under short-day conditions (9 hours light/15 hours dark). We optimized the growth conditions for shortening the period of soybean generation progression based on speed breeding. The optimizing conditions are as follows. (1) Irradiation using LED light source for 9 hours, (2) 506 μmol/(m2ㆍs) of PPFD at 30 cm from the ground, (3) Planting density of 5 cm × 5 cm, (4) temperature of 25°C ± 2°C and (5) humidity of 50% ± 10%. If this condition is used, soybeans can be advanced by one generation within an average of 73 days. It is possible to advance five generations a year using only indoor speed-breeding system. Furthermore, if it includes the development of lines in the field, four generation per year, which is advance three generations using indoor speed-breeding system and one generation in the field, is allowed to increase soybean breeding speed with minimum input.