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Soybean (Glycine max [L.] Merr.) was domesticated from the wild annual progenitor Glycine soja (Sieb. & Zucc.) in the temperate zone of China. Through domestication and improvement, soybean agronomic traits and adaptability have been significantly altered. In this review, we discuss the ways in which genetic changes were selected in soybean to enable adaptation to diverse environmental conditions. Challenges and strategies are discussed for breeding new elite varieties from existing elite varieties. Finally, we propose a strategy to break the current genetic bottleneck in soybean breeding: de novo domestication, which utilizes the excellent genetic resources available in wild soybean and provides a feasible strategy for accelerating the soybean improvement process. Overall, this review serves as a guide to understand the genetic factors that have driven soybean domestication and improvement over thousands of years, promoting future generation of soybean cultivars that are optimized for high yield under stressful environmental conditions. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max) is a typical short‐day plant, but has been widely cultivated in high‐latitude long‐day (LD) regions because of the development of early‐maturing genotypes which are photoperiod‐insensitive. However, some early‐maturing varieties exhibit significant responses to maturity under different daylengths but not for flowering, depicting an evident photoperiodic after‐effect, a poorly understood mechanism. In this study, we investigated the postflowering responses of 11 early‐maturing soybean varieties to various preflowering photoperiodic treatments. We confirmed that preflowering SD conditions greatly promoted maturity and other postflowering developmental stages. Soybean homologs of FLOWERING LOCUS T (FT), including GmFT2a, GmFT3a, GmFT3b and GmFT5a, were highly accumulated in leaves under preflowering SD treatment. More importantly, they maintained a high expression level after flowering even under LD conditions. E1 RNAi and GmFT2a overexpression lines showed extremely early maturity regardless of preflowering SD and LD treatments due to constitutively high levels of floral‐promoting GmFT homolog expression throughout their life cycle. Collectively, our data indicate that high and stable expression of floral‐promoting GmFT homologs play key roles in the maintenance of photoperiodic induction to promote postflowering reproductive development, which confers early‐maturing varieties with appropriate vegetative growth and shortened reproductive growth periods for adaptation to high latitudes. Summary statement: The photoperiodic after‐effect of early‐maturing soybean varieties is caused by the maintenance of high‐level expression of floral‐promoting GmFTs. This phenomenon indicates that maturity exhibits a stronger photoperiod sensitivity than flowering time, which ensures an appropriate vegetative growth and shortened reproductive growth of early‐maturing soybean varieties to adapt to high latitudes with significant changes in photoperiods from long day to short day in the growing season. [ABSTRACT FROM AUTHOR]