Evaluation For Cold Tolerance In Germplasms Of Vitis Amurensis And Study On Mechanisms Of Cold Tolerance

Amur grape（Vitis amurensis Rupr.）is one of the most cold-tolerant grape species and important materials for cold-tolerant breeding.But there were some differences in cold tolerance among germplasms basing on field investigation.Because of lacking on the available methods to evaluate the cold tolerance of amur grape,and unclear mechanisms of its cold tolerance,so further excavation and utilization of this cold-tolerant germplasm is affected.In order to solve these problems,the specific research is carried out and the related results as follows:1.The TTC staining indexes of the amur grape shoots under low temperature treatments could fitted well with a typical inverted S-shape curve.The fitting degrees of 40 amur grape germplasms were from 0.9564 to 0.9993,and the low semi-lethal temperature value(LT₅₀)of each germplasm was determined by fitting TTC staining indexes with logistic equation.Correlation analysis indicated that the LT₅₀ values with the average subordination values and field germination rates were significantly negative correlated,the correlation coefficient was﹣0.88303 and﹣0.87670,respectively.It suggested that the pictorial assessment of TTC staining image can be used as a quick and convenient method to accurately evaluate the cold-tolerant of amur grape germplasms at dormancy stage.2.The cold resistance of 30 intraspecific amur grape germplams collected from different areas were evaluated for two consecutive years by the above method.The cold tolerance of these germplams were different that the range of the average LT₅₀ was from-40.4℃to-26.8℃.According to the LT₅₀values,V.amurensis‘Zuoshan-2’collecting from Heilongjiang province was assigned to hardiness 1,is the most cold-tolerant germplasm;24 germplasms that collected from Heilongjiang,Jilin and Liaoning provinces respectively were subjected to hardiness 2;3 germplasms collected from Hebei province belonging to hardiness 3;V.amurensis‘201309’collecting from Hebei province was divided into hardiness 4.So the cold tolerance of amur grape germplasms could be related to their geographical distributions.3.The cold tolerance of shoots increased gradually when the natural temperature decreases in autumn,reached its peak of cold tolerance at natural dormancy period of November.The cold tolerance remained unchanged in January though entering the passive dormancy period.The different contents of fructose,glucose and trehalose in soluble sugars and bound water played a crucial role in the different cold tolerance of amur grape shoots at dormancy period.The endogenous hormones also have some effect in regulating the cold tolerance of amur grape.While the difference in leaf damage of amur grape under the low temperature stress may be deeply correlated with the NPQ values and the higher SOD and APX activities.Thus it can be seen that the amur grape may have different response mechanisms to low temperature stress under different annual periods.4.The transcriptome library on the phloem and xylem of amur grape during overwintering was constructed and analyzed.The result showed that the effect of low temperature exercise on the phloem and xylem of amur grape mainly reflects in the process of biology;MAPK signaling pathways and the starch-sucrose metabolism pathways were involved in low temperature response mechanisms.The differential genes in MAPK signaling pathways mainly regulate the expression of PP2C and SnRK2,further impact on the sugar metabolism and ABA accumulation;meanwhile in starch-sucrose metabolism pathways largely mediated trehalose metabolism,thus strengthened the capacities of binding with water and protecting cell membrane or protein from cold stress.These results also provide evidence for the physiological mechanism on the relationship between glycometabolism and endogenous hormones in phloem and xylem with cold tolerance of amur grape shoots.At the same time,the differential expression of gene encoding WRKY33 transcription factor also provides a new direction for the study on cold tolerance mechanism of amur grape.