Salt Tolerance Of Rice At Seedling Stage And Its Response To Temperature

Excessive soil salinity and abnormal climate are the key factors restricting the high yield of crops.As an important crop,rice is often subjected to salt stress,meanwhile;temperature as a necessary condition for plant growth,is a necessary factor in the study of plant physiology.The existing researches mainly focus on the comprehensive stress resistance of rice to cold or heat stress and salt stress,and there are few studies on their interaction..In this study,two indica rice varieties with stronger(Yandao 3931)and weaker(Xiangwanxian 1)salt tolerance and two japonica rice varieties with stronger(Wulinggeng 1)and weaker(Liaogeng 371)salt tolerance were used as experimental materials in the previous experiment.The experiment was conducted at 32℃(day)/27℃(night),28 ℃(day)/23℃(night)and 24℃(day)/19℃(night),respectively.The seedlings were treated with 0.8%NaCl at the time of three leaves.The physiological indexes of the three treatment groups and their control groups of the above four varieties were measured on the 2nd,4th,6th and 8th days after salt treatment to explore the physiological mechanism of salt tolerance at seedling stage of the four varieties under different temperatures.This study laid a foundation for further exploring the relationship between salt tolerance and temperature in rice.In addition,this study selected Yandao 3931 with the strongest salt tolerance among the four varieties for transcriptome sequencing,and compared the differentially expressed genes(DEGs)between salt treatment and control group,and between salt treatment and salt treatment at three different temperatures,to explore the molecular regulation mechanism of salt tolerance in rice seedling stage and its response to temperature.The main results are as follows:(1)Taking chlorophyll content,dead leaf rate,mortality rate and proline content as reference,salt tolerance of the four varieties was significantly decreased at 32℃(day)/27℃(night).The results showed that at 24℃(day)/19℃(night)could promote the activation of salt tolerance mechanism.(2)Biomass,root shoot ratio,root activity,enzyme activity and other indicators were closely related to variety specificity,and there was no uniform regular of salt tolerance.Yandao 3931 showed excellent salt tolerance at 28℃(day)/23℃(night)and 24℃(day)/19℃(night),and still had a high survival rate on the 8th day after salt treatment.(3)Six common DEGs were identified from the cross of DEGs between the control group and salt treatment groups under three temperature conditions.The six genes were annotated into the NR database.Three common up-regulated genes encoded heat stress transcription factor A-6a,BAG family chaperone regulator 6 isoform X2 and bidirectional sugar transporter SWEET 15,respectively.The three down regulated genes encoded high-affinity nitrate transporter-activating protein 2.1,cation transporter HKT7 isoform X1,and protein LOC4350169.(4)The GO analysis of DEGs between the control group and salt treatment group showed that the expression of genes related to salt stress response was active under relatively low temperature.4,4 and 32 DEGs response to salt stress genes were annotated at 32℃(day)/27℃(night),28℃(day)/23℃(night)and 24℃(day)/19℃(night),respectively.(5)In the analysis of KEGG pathway enrichment of DEGs between control group and salt treatment group of Yandao 3931 at three temperatures,13 pathways were enriched at the same time.These 13 metabolic pathways were closely related to the resistance of rice to salt stress,which provided a direction for future research on salt tolerance pathway in rice.This study explored,compared and analyzed the salt tolerance of four representative varieties at Seedling Stage under three groups of different temperature conditions,which provided new ideas for further research on salt tolerance mechanism of riceIn this study,the salt tolerance of four representative varieties was studied,compared and analyzed under three groups of different temperature conditions,which provided new ideas for further research on the mechanism of salt tolerance in rice,and had important significance for salt tolerant rice breeding.