Modified speed breeding approach reduced breeding cycle to less than half in vegetable soybean [Glycine max (L.) Merr.].

Vegetable soybean [Glycine max (L.) Merr.] is gaining popularity because of its high nutritive values and health benefits; however, its productivity is scarce. Recognizing the need to accelerate breeding progress, a modified approach of 'speed breeding' was used in 16 vegetable soybean genotypes to reduce the breeding periods. The genotypes were exposed to cycles of 10 h light (30 °C) and 14 h dark (25 °C) with CO2 (550 ppm) and without CO2 supplementation under the light intensity of 220 µmol m-2 s-1 at the canopy level and 70-80% relative humidity. To reduce the time further, physiologically matured pods were harvested once they changed their color from green to greenish yellow and dried in the oven for 7 days at 25 ± 2 °C with RH 10-20%. The genotypes showed variable responses towards days to flowering coupled with an increase in the number of pods, number of seeds and seed weight per plant, and 100 seed weight during a short breeding period under CO2 supplement. A couple of genotypes behaved indifferently under normal and elevated CO2 levels. The fresh oven-dried seeds displayed 73.33-100% germination, while that in the seeds stored at 4 °C for 10 months was 80-100%. Thus, the modified speed breeding technique could effectively reduce the breeding period without affecting the germination of the seeds. With this approach, we could save 6-34 days in a genotype dependent way which would at least give 4-4.5 generations of soybean per year instead of the usual 1-2 generations. Further, the reduction in maturity duration was more in longer duration genotypes than the shorter duration ones. This represents the country's initial report of rapid breeding in vegetable soybean and offers ample opportunity for rapid generation advancement in this crop. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-024-01503-z.

Identification of quantitative trait loci (QTLs) and candidate genes for seed shape and 100-seed weight in soybean [Glycine max (L.) Merr.].

Seed size and shape are important traits determining yield and quality in soybean. Seed size and shape are also desirable for specialty soy foods like tofu, natto, miso, and edamame. In order to find stable quantitative trait loci (QTLs) and candidate genes for seed shape and 100-seed weight, the current study used vegetable type and seed soybean-derived F2 and F2:3 mapping populations. A total of 42 QTLs were mapped, which were dispersed across 13 chromosomes. Of these, seven were determined to be stable QTLs and five of them were major QTLs, namely qSL-10-1, qSW-4-1, qSV-4-1, qSLW-10-1, and qSLH-10-1. Thirteen of the 42 QTLs detected in the current study were found at known loci, while the remaining 29 were discovered for the first time. Out of these 29 novel QTLs, 17 were major QTLs. Based on Protein Analysis Through Evolutionary Relationships (PANTHER), gene annotation information, and literature search, 66 genes within seven stable QTLs were predicted to be possible candidate genes that might regulate seed shape and seed weight in soybean. The current study identified the key candidate genes and quantitative trait loci (QTLs) controlling soybean seed shape and weight, and these results will be very helpful in marker-assisted breeding for developing soybean varieties with improved seed weight and desired seed shape.