Speed breeding by artificial control of photothermal conditions facilitates generation advancement but was limited in scale and cost. In this study, we demonstrated a cost-saving off-site summer nursery pattern, taking full advantage of shorter daylength and higher temperature with lower latitude compared to the origin of the soybean cultivars used in the study. This substantially reduced the generation cycles under totally natural conditions. Using this approach, two generations of soybean cultivars from Northeastern Spring Planting Region (NE) and Yellow-Huai-Hai Valleys Summer Planting Region (YHH) were successfully obtained in Beijing and Hainan, respectively, compared to one generation in origin. Fresh-seeding method was also used to further shorten the generation duration by 7–10 days, thereby allowing at least four generations per year. Using DNA markers to define haplotypes of maturity genes E1–E4, we proposed a model to predict the optimum adaptation region of the advanced generation lines. Taken together, we present a speed-breeding methodology combining off-site nursery, fresh-seeding method, and marker-assisted selection, aimed at accelerating soybean improvement.

The anomalies of electric-magnetic field and self-potential before earthquakes are important precursory phenomena. A simulating experiment study on the variations in ultra-low frequency (ULF) magnetic field and self-potential during rock cracking was carried out in a magnetic field-free space. The results revealing in detail the whole process of the occurrences of electric and magnetic anomalies are significant for understanding the microscopic mechanism of ULF electric and magnetic signals. The experiment indicated that at the initial stage the slow changes in strain, self-potential and magnetic field with small amounts appeared firstly near the source of initial cracking, and then extended as the crack developed on. In the time domain, the self-potential anomaly emerged first and ULF magnetic field changes arose then. The shape of the ULF electric and magnetic anomaly varied obviously in early-, mid-and late-term of the test. The authors attributed the pulse-like changes of self-potential to the generation and movement of the accumulated electric charges during the cracking caused by charge separation on the crack tips within the sample. While the magnetic pulses of shorter-period at the last stage of the test, may be induced by instantaneous electric current of the accumulated charge during the cracking acceleration. The technical method and the observational results of this experiment are given in detail and the microscopic mechanism of electric and magnetic precursors before earthquake are discussed in the present paper as well.

An experiment on self‐potential (SP) and strain changes during elastic deformation and fracture of rock samples was conducted by means of a biaxial servo‐control loading‐machine and a detecting array of strain gauges and electrodes. Some correlated and widespread pulse‐like transient variations in self‐potential and strain‐field appeared at some special situations, including sudden loading/ unloading, stick‐slip and fracture of rocks. The results indicate that though sometimes the stress ‐ is rather high, there is no SP anomaly occurring if the stress change‐rate γ = dσ/dt equals zero or keeps positive or negative constants. On the contrary, at the moment changes suddenly the pulse‐like SP change γV will always arise no matter the increment Δ;γ is positive or negative. The positive or negative sign of Δγ gives opposite effect on ΔV. The anomalous amplitude of ‐V is proportional to that of Δγ. The observed clear temporal and spatial self‐potential changes at the moment of sudden stress‐rate change and rock fracture mean that it is possible to detect the precursory and co‐seismic electric and corresponding strain variations if the above‐mentioned conditions can be met near a seismogenic zone. It is a support to the seismic precursory research of self‐potential and strain.

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