The Evaluation And Response Of Low Temperature Tolerance Of Cotton Varieties In Huanghuai Area During Seed Germination

Cotton is a high-temperature crop,and is sensitive to low temperature in the germination.In recent years,as labour costs have risen,cotton production has been transformed into light and simplified(LSC)model.LSC model includes intensive sowing.It puts forward higher demands on the quality of cotton.Therefore,it is of great significance and effect to improve the low temperature tolerance of cotton seed germination.Now,most of the research on low temperature stress of cotton is concentrated in seedling stage.This study evaluated the low temperature tolerance of 38 cotton varieties from several aspects.At the same time,this paper studies the physiological and molecular level of the cryogenic mechanism.It is of great significance to the selection of low temperature varieties of cotton.This test is based on 38 cotton varieties which are now or used to be widely planted in Huanghuai Area,and studied the germination index of different low temperatures(18℃,15℃,12 ℃).The control temperature was 25 ℃.This paper evaluated their ability of low temperature tolerance.On the basis of evaluation of cotton varieties resistant to low temperature,four varieties were screened(SRCR37,SCRC36,Stonville2 B,Stonville5A).Under low temperature stress(25℃,18℃,15℃,12℃),and different period of germination(0h,12 h,24h,36 h,48h),we picked the germinated seeds for the material.However,the gene expression material is the seed of 12 ℃ low temperature germination.It provided to theoretical basis and germplasm resources for the new cotton varieties with low temperature germination.The main results were as follows:1.The difference tolerance ability of 38 cotton variety in germination period under low temperature stress.As the temperature decreased,the germination rate,germination index and vigor index showed a decreasing trend in all cotton varieties.There were a significantly difference between them.Principal component analysis showed that the three integrated principal components represented 86.664% of the original data of the tested varieties.Cluster analysis indicated that 38 varieties were divided into three categories: strong resistance varieties,resistant varieties and non-resistant varieties.The early introduced varieties and the varieties bred with early introduced germplasm resources showed weaker resistance in response to low temperature stress.The new transgenic insect-resistant cotton varieties(SRCR37,SCRC36)showed a stronger advantage under low temperature stress.2.The changes of physiological indexes on cotton seed germination under low temperature stress.Under low temperature stress,MDA content was increased compared with the control,and the trend was increase as the temperature decreased.The MDA content of resistant varieties is lower than that of non-resistant varieties.The anti-oxidase and Osmotic regulation substances increased with the lower stress temperature.The activity of resistant varieties is higher than that of non-resistant varieties.The research shows that SRCR37,SRCR36 have more sensitive rapid adjustment ability,system of cell membrane peroxidation,smaller cells ROS removal ability is strong,have stronger resistance to low temperature germination ability.3.The changes of cold resistance gene expression on cotton seed germination under low temperature stress.A large number of downstream factors are expressed through the CBF(C-repeat bingding transcription factor)gene in the process of plant resistance,in order to improve the cold resistance of plants.According to the report,the CBF family includes CBF1,CBF2,CBF3,CBF4,CBF5,CBF6.The results of the study showed that the members of CBF1,CBF2,CBF4 and CBF6 were all involved in the low temperature stress response.The expression of four genes raised in SCR37 and SCR36.In the duress of 12 h,they were the peak of the expression.In Stonville2 B,Stonville5A,they were not obvious that the expression of four genes.This paper shows that the SCR37 and SCR36 are more sensitive to the cold response,thus showing the strong resistance to low temperature.