Comparison Of Photothermal Responses Among Different Ecotypes Of Soybean In China And The Analysis Of GmFT Gene Expression

Soybean (Glycine max [L.] Merr.) is a short-day crop which favors temperate weather, thus, short day (SD) and high temperature (HT) may promote its growth and development. Previous studies showed that photoperiod and temperature (photothermal) exert different effect on growth and development of soybean cultivars from different ecological regions. To define the photoperiodic, thermal and photothermal interaction effects on the soybean from different ecological regimes, to discover their effects on growth and inter-relationship of them, three photoperiodic treatments of natural day length, 12h (short day or SD) and 16h (long day or LD) were conducted and integrated with two thermal conditions, HT (sown in the summer in Beijing) and low temperature (LT) (sown in the spring), i. e., combinations of LD+ LT, LD+ HT, SD+ LT and SD HT were performed. Using 15 control cultivars of the national soybean cultivar regional trials as materials, photothermal responses of them were investigated. In addition, varietal variations in agronomic, productive and quality traits grown in different photothermal combinations were analysized.GmFT is a key gene for soybean photoperiodic reaction, and the expression level and pattern of this gene are regulated by photoperiodism. In order to make a further illumination of the inter-relationship of photoperiod and temperature in soybean growth and development, soybean cv. Heihe 27 and Zigongdongdou (ZGDD) which are insensitive and sensitive to photoperiod, respectively, were treated with different photothermal combinations in phytotrons. The relationship of GmFT expression and photothermal response was analysized.The main results are summarized as below:1. Sensitivity of photoperiod response prior to flowering as well as post-flowering, in addition to post-effect of SD before flowering, is strongly kept in agreement between different soybean ecotypes. In addition, sensitivity of photoperiod response of varieties is stable during emergence and physiological maturity. SD hastened the reproductive development, and LD hastened vegetative growth. Photoperiod response sensitivity before flowering and of different soybean ecotypes decreased as follows: Summer Sowing Soybeans from South, Summer Sowing Soybeans from Yellow-Huai-Hai River Valleys, Spring Sowing Soybeans from South and Spring Sowing Soybeans from North.2. Higher temperature hastened the development of soybean from sowing to blossoming. The order of thermal sensitivity before flowering in soybean ecotypes are as below: Summer Sowing Soybeans from South > Spring Sowing Soybeans from South > Spring Sowing Soybeans from North > Summer Sowing Soybeans from Yellow-Huai-Hai River Valleys. High temperature promoted seed germination and emergence, and shorted the time from sowing to emergence. In terms of time from sowing to emergence, there is no significant difference between varieties collected from different ecological regions.3. Obvious interaction effects of photoperiod and temperature on soybean development were found in this study. Higher temperature enhanced the promotion effect of short day on development; while low temperature weakened this effect. Short day may enhance the promotion effect of higher temperature to development; while LD may weaken the effect. The promotion effect of elevated temperature on photoperiod response sensitivity, as well as the promotion effect of shorted day length on thermo response sensitivity, decreased as altitude of cultivar regimes.4. LD and high temperature led to a higher number of node to first flower, plant height, pod height at bottom, node number of main stem. Photoperiod response sensitivity of the number of node to first flower, plant height, pod height at bottom and node number of main stem in soybean varieties decreased as follows: Spring Sowing Soybeans from South > Summer Sowing Soybeans from Yellow-Huai-Hai River Valleys >Summer Sowing Soybeans from South > Spring Sowing Soybeans from North. As to the varieties that may be mature under LD, LD increased the pod number, seed number and seed weight per plant; SD treatment increased the seed weight of 100 seeds of soybean varieties from Spring Sowing Soybeans from North and Yellow-Huai-Hai River Valleys; but decreased the seed weight of 100 seeds of the Summer Sowing Soybeans from South; and no significant effect on Summer Sowing Soybeans from South. Photoperiod response sensitivity of productivity per soybean plant of different ecological regions decreased as Spring Sowing Soybeans from South > Summer Sowing Soybeans from Yellow-Huai-Hai River Valleys > Summer Sowing Soybeans from South > Spring Sowing Soybeans from North. LD led to a protein quantity of Spring Sowing Soybeans from North, however slightly increased the protein quantity of varieties from Spring Sowing Soybeans from North and Summer Sowing Soybeans from North. LD treatment after flowering in addition to SD before flowering led to a increased the protein content of varieties from Spring Sowing Soybeans from North, nevertheless, a decreased the protein content of varieties from Spring and Summer Sowing Soybeans from South. SD treatment increased the fat acid content of varieties from Spring Sowing Soybeans from North, from Yellow-Huai-Hai River Valleys and Summer Sowing Soybeans from South. LD treatment after flowering in addition to SD before flowering led to a decreased fat acid content of varieties from Spring Sowing Soybeans from North, from Yellow-Huai-Hai River Valleys, while fat acid content of varieties from Spring and Summer Sowing Soybeans from South increased. Total protein and fat acid content varieties from Spring Sowing Soybeans from North decreased as day length shortened, and it is opposite to varieties from Summer Sowing Soybeans from South.5. GmFT is a member of FT-like sub-family in PEBP gene family, and exhibited similar function as FT that promotes flower initiation in model plant of Arabidopsis. Expression of GmFT in photoperiod-sensitive cv. ZGDD was promoted by SD, as well as lower temperature. However, under LD condition, temperature did not affect the expression apparently. Photoperiods did not affect the expression of GmFT in Heihe 27, but HT may increase the expression of GmFT in this photoperiod-insensitive soybean variety.