Effects of temperature regimes on seed germination and early growth of different soybean cultivars

High temperature is an important global issue that impedes agricultural production, especially of soybean (Glycine max [L.] Merr.) crop. Numerous studies were undertaken to estimate the effect of temperature on soybean seed germination under low temperatures. However, the effects of high-temperatures on seed germination and early seedling establishment of various soybean cultivars need to be explored further. Therefore, the current study was performed in growth chambers to evaluate genetic variations among different soybean cultivars for germination and early growth under varying temperatures. Five temperatures, i.e., 15, 20, 25, 30, and 35 ◦C, and four soybean cultivars (PI408105A, PI567731, PI567690, and PI416937) were used. The results showed that soybean cultivars revealed substantial variations in germination percentage (GP), germination rate index (GRI), germination energy (GE), seed vigor index (SVI), and seedling length under different temperatures mentioned above. The results indicated that higher temperature [35 °C] inhibited seed germination. Conversely, the intermediate temperatures [20, 25, and 30 ◦C] depicted good germination. Lower temperature declined the seed germination to some extent, and the germination percentage of PI408105A, PI567731, PI567690, and PI416937 were observed as 63.33%, 56.67%, 50%, and 40.11%, respectively. For all the soybean cultivars, the mean seed germination rate was maximum at 25 ◦C. However, the germination rate index continued to increase until 30 ◦C . The soybean cultivar PI408105A was the most promising under high temperature, exhibiting higher GP by 86.67%, highest SVI by 50.95%, and GRI by 50% at 30 ◦C. In contrast, PI416937 was among the cultivars sensitive to high temperature and showed a higher germination rate only at 20 ◦C. The seeds of PI408105A, PI567731, and PI567690 can germinate well under intermediate temperature conditions, making them a promising species for use in hot climatic zones. According to the current findings, it was concluded that soybean should be planted under mild temperatures for good crop stand and production. Moreover, it is recommended that cultivars such as PI408105A could be grown in warm conditions.