Accelerating Soybean Breeding in a CO2-Supplemented Growth Chamber

Abstract

Soybean (Glycine max) is the most important dicot crop worldwide, and is increasingly used as a model legume due to the wide availability of genomic soybean resources; however, the slow generation times of soybean plants are currently a major hindrance to research. Here, we demonstrate a method for accelerating soybean breeding in compact growth chambers, which greatly shortens the generation time of the plants and accelerates breeding and research projects. Our breeding method utilizes commonly used fluorescent lamps (220 µmol m-2 s-1 at the canopy level), a 14-h light (30 °C)/10-h dark (25 °C) cycle, and carbon dioxide (CO2) supplementation over 400 ppm. Using this approach, the generation time of the best-characterized elite Japanese soybean cultivar, Enrei, was shortened from 102-132 reported in the field to just 70 days, thereby allowing up to 5 generations per year instead of the 1-2 generations currently possible in the field and/or greenhouse. The method also facilitates the highly efficient and controlled crossing of soybean plants. Our method uses CO2 supplementation to promote the growth and yield of plants, appropriate light and temperature conditions to reduce the days to flowering, and the reaping and sowing of immature seeds to greatly shorten the reproductive period. Thus, the appropriate parameters enable to accelerate soybean breeding in the compact growth chambers commonly used for laboratory research. The parameters used in our method could therefore be optimized for other species, cultivars, accessions, and experimental designs to facilitate rapid breeding in a wide range of crops.

Predicted genetic gains from introgressing chromosome segments from exotic germplasm into an elite soybean cultivar

“…Altogether, it would take 5-6 generations to pyramid two LGs into IA3023. Targeted introgression can be shortened through winter nurseries (Pham, Shannon and Bilyeu 2012) or CO 2 supplemented growth chambers that enable up to five generations of soybean each year (Nagatoshi and Fujita 2018). We plan to conduct empirical experiments to assess the gains from introgressing ≤4 LGs from one of the PIs into IA3023.…”

Hydroponic Systems for Arabidopsis Extended to Crop Plants

“…Complete enclosure of the growing crop is one of the features of recent speed breeding technologies [38,39,43]. Soybeans grown hydroponically using NFT in the completely enclosed bioregenerative life support systems have a 110-133 day Hydroponic Systems for Arabidopsis Extended to Crop Plants DOI: http://dx.doi.org /10.5772/intechopen.89110 generation time [32].…”

“…Soybeans grown hydroponically using NFT in the completely enclosed bioregenerative life support systems have a 110-133 day Hydroponic Systems for Arabidopsis Extended to Crop Plants DOI: http://dx.doi.org /10.5772/intechopen.89110 generation time [32]. Soil grown soybeans have a generation time of 132 days, but growing them in an enclosed system with elevated carbon dioxide decreases the generation time to 70 days [43]. Combining hydroponics of crop species with other technologies of speed breeding might produce even shorter generation times or higher yields and seed viability.…”

“…However, other kinds of plant growth promoting microbes (PGPMs), including some of those tested in hydroponic systems with Arabidopsis [28], produce higher photosystem II efficiency in hydroponically-grown soybean plants [45]. This could be beneficial in speed breeding, which improves with improved photosynthesis achieved with elevated carbon dioxide [43]. Those plants grown to maturity in enclosed hydroponics and inoculated with PGPMs show stabilized microbial communities over time [46].…”

Impacts of genomic research on soybean improvement in East Asia

“…Thus, crossing of distinct varieties would require careful planning to match the flowering time of the two parental lines and to maximize the number of generations per year. To solve these problems, a soybean breeding protocol using CO 2 -supplemented growth chambers has greatly shortened the time of each breeding cycle from over 100 days to around 70 days (Nagatoshi and Fujita 2019). The protocol shortens the flowering time by controlling the light/dark cycle and temperature and improves flower number and quality to increase crossing efficiency by supplementing the plant with CO 2 and by reducing the seed-to-seed period by growing immature seeds (Nagatoshi and Fujita 2019).…”