Study Of Physiological And Biochemical Characteristics Under Low Temperature Stress And Expression Of Cold-Related Transcription Factors In Grafted Watermelon

In recent years,the North China area gradually formed hebei Le Ting,yellowinside,henan,shandong qingzhou such as early-maturing watermelon production areas.The main producing areas of watermelon seedlings are often affected by low temperature freezing injury,which seriously influenced watermelon production.Most of the people widely used pumpkin grafting to improve the cold resistance of watermelon.Although the predecessors to improve cold resistance of watermelon pumpkin grafting have already done a lot of research,many are focused on the physiological and biochemical characteristics and its molecular mechanism is still not clear.The experiment with watermelon seedling,watermelon and grafted watermelon seedling,watermelon and pumpkin grafted seedlings as materials,systematic study of the low temperature stress on physiological and biochemical characteristics of watermelon seedlings and low temperature stress under different materials MYB transcription factor expression,to explore the molecular mechanism of cold resistance of grafted watermelon.The specific test results are as follows.1.Effects of low temperature stress on physiological and biochemical indexes of watermelon seedlings with different materials:MDA content in all processing of watermelon seedlings after low temperature stress were sharp rise and decline,the process of low temperature stress shows that watermelon seedlings after low temperature treatment,the cell membrane by a certain degree of damage,then as to adapt to stress,could trigger a defense reaction cell membranes and results in the decrease of malondialdehyde content.The content of MDA reached the maximum value in 24 h.In the low temperature stress treatment,the MDA content of the root were higher than those of grafted seedlings.That grafting membrane damage is lower than watermelon from the root,also suggests that grafting ratio since the seedling resistance to low temperature.Low temperature stress under all treatment of proline content of watermelon seedlings change increased first and then decreased trend.Under low temperatures reach maximum when at 48 h,but the watermelon watermelon grafting in unprocessed proline content is lower than the seedling,the stress of watermelon watermelon grafting proline content rise sharply,in dealing with about 20 h proline is higher than the root and watermelon after grafting.After a period of low temperature after adaptation,grafting proline content were higher than the seedling,showed that grafting ability to resist chilling injury stress significantly is higher than the root.Grafting under low temperature stress and soluble sugar content were higher than the root is on the rise,showed that grafting energy metabolism is more vigorous,provides more nutrients for plants.At the same time to maintain stability of cell membrane,thus has cold resistance was stronger than the root.Under low temperature stress,SOD content of watermelon pumpkin Grafted and watermelon grafted watermelon seedlings was always higher than that of self rooted seedlings.Consistent trends are first rise after the fall.CAT content in watermelon watermelon grafting and watermelon pumpkin after grafting under low temperature stress,showed a trend of first rise then fall.CAT content inwatermelon watermelon grafting is the highest.The second content is watermelon pumpkin grafting.The lowest content of is watermelon seedling.POD content in watermelon watermelon grafted seedlings has been gradually increased,watermelon pumpkin grafted seedlings overall also showed an upward trend.Watermelon seedling 24 h wasdecreased,48 h and 72 h were increased.In the low temperature stress,the content of POD is the lowest in watermelon seedling.The change of SOD,CAT and POD that grafting seedling's resolve with the strong ability of oxygen anion,so as to better protect plants against external stress.Expression of MYB transcription factors in different materials under low temperature stress.Cla017850,Cla009263,Cla022152,Cla21419 are all belong to MYB transcription factors.After low temperature treatment,the expression of Cla017850 gene in watermelon seeding was increased first and then decreased.Cla017850 gene watermelon watermelon grafting and pumpkin grafted seedlings expression trend is consistent.all showed a trend of first increased and then decreased and increased,after 24 hourlow-temperature stress reachedmaximum,including Cla017850 gene in watermelon watermelon grafting expression quantity to rise sharply,9.56 times that of the basic value 0h,and watermelon pumpkin grafting in the treatment of the 24 h express quantity is 2.79 times that of the basic value 0h.In the treatment of 48 hand 72h after its amount of express were higher than control.Watermelon watermelon grafting in low temperature processing variety expression quantity are the highest.Speculated that this may participate in the defense mechanism of plants to cold.After low temperature treatment,Cla009263 gene in watermelon seedling expression showed a trend of rise after falling first,watermelon watermelon grafting and grafting watermelons pumpkins Cla009263 gene expression trend is consistent,all showed a trend of decline after rising first and reach maximum in 48 h after low temperature stress processing,including watermelon watermelon grafting Cla009263 gene expression quantity to rise sharply,4.12 times that of the basic value is 0h,and watermelon pumpkin grafting in the treatment of 48 h express quantity is 4.375 times that of the basic value 0h.In the treatment of 48 hour and 72 hour after its amount of express were higher than control.The molecular mechanism remains to be further research later.After low temperature treatment,Cla022152 gene in watermelon seedling and grafting watermelons pumpkins expression of transcription factor quantity is increased before they are falling.The watermelon seedling peaked in low temperature stress treatment after 24 hour,this may participate in the defense mechanism of plants to cold.Cla022152 gene in watermelon watermelon grafting showed a trend of rise after falling first,after 48 hour to the lowest in low temperature stress processing,including watermelon watermelon grafting Cla022152 gene expression quantity fell sharply,0.13 times that of the basic value is 0h,in the treatment of 48 hour and 72 hour after the express quantity are lower than controls.Cla021419 gene in watermelon seedling expression showed a trend of decline after rising first,watermelon watermelon grafting and grafting watermelons pumpkins Cla021419 gene expression trend is consistent,all showed a trend of rise and fall after fall first,watermelon watermelon grafting in low temperature stress treatment after 72 h,the lowest one Cla021419 gene in watermelon watermelon grafting expression quantity fell sharply,0.18 times that of the basic value is 0h,and watermelon pumpkin grafting in the treatment of the 24 h express basic value 0h is the minimum amount of 0.02 times.Watermelon pumpkin grafting in the treatment of 48 hour and 72 hour after the express quantity were higher than control.