Evaluation of Seed Germination of Main-cultivated Cotton under Low Temperature in Northern Xinjiang in Recent Ten Years

【 Objective 】 In order to understand the effect of low temperature on seed germination and to explore the suitable methods for identifying chilling tolerance of cotton seeds.【 Method 】Some mainly-cultivated cottons were selected as the experimental materials in northern Xinjiang in recent ten years, responses of seed germination characteristics to different temperature were studied, and their germination abilities were also evaluated using germination parameters and relative germination parameters (cold tolerance coefficient)according to subordinative function method under low temperature, respectively.【 Result 】With the increase of stress, the germination ability of cotton seeds was significantly inhibited, the average seed germination rate decreased with the increase of the temperature, and other indexes of germination were significantly higher with the increase of the temperature. The cold resistant germination ability of cotton seeds was positively correlated with the tested germination index. At the same low temperature, two kinds of subordinate function method showed a good agreement on the seed germination ability at low temperature, but the germination rate of cotton seed under different low temperature was different. The seed germination of Zhongmiansuo No.36 and Xinluzao No.46 had a high chilling-tolerance at 15℃, and at 25℃, those with high chilling tolerance were Xinluzao No.25, Xinluzao No.42, Xinluzao No.36, Xinluzhong No.26, Zhongmiansuo No.36, Xinluzao No.41 and Xinluzao No.35. Except for the average germination speed, the relationship among others germination parameters and seed germination ability was significantly correlated. The identification model for cold resistant cotton seed germination under low temperature was established by stepwise regression method: Y=0.01+0.022^* GI (germination index) (R²=0.998) at 15℃; Y=-0.046+0.002^* GR (germination rate) +0.005^* SGC (Seed germination coefficient) (R²=0.992) at 12℃. 【 Conclusion 】The seed of Zhongmiansuo NO.36 and Xinluzao NO.46 had a high chilling tolerance at the seed germination stage. The germination index of fuzzy membership function method can be effectively used for the identification and evaluation of cold tolerance based on cotton seed germination.