| Morinda citrifolia Linn,also known as Morinda citrifolia,is called NONI in western countries and is a plant of the genus Morinda.As a broad-spectrum plant source,Morinda citrifolia has been developed into a health food or nutritional supplement because of its rich nutrition and functional ingredients.The product has a good market development prospect.However,due to the characteristics of the typical tropical plants of the Morinda citrifolia,the varieties cultivated on the current production are not resistant to cold,so the cultivation of the Morinda citrifolia in Hainan is limited to the South of the region,and its promotion area is greatly limited.At the same time,extreme cold weather in Hainan in winter often has fatal effects on the production of Morinda citrifolia.Cold damage has become a bottleneck that severely restricts Morinda citrifolia production.It is of great theoretical and practical significance to carry out the cold-resistance physiological studies of Morinda officials,to screen for cold-resistant germplasm,to explore excellent cold-resistant genes,and to breed cold-tolerant varieties.According to the search,no related reports on the cold-resistance of Morinda citrifolia have been found so far.Therefore,this study intends to use the collected Morinda citrifolia germplasm with cold-resistant seedlings to carry out cold-resistance physiology research of Morinda citrifolia.The membership function was used to analyze and compare the cold resistance ability and physiological index of Morinda citrifolia seed germplasm.The cold-resistance genes were screened in the transcriptome by comparing the difference coding genes.This study provides a theoretical basis for the cold-resistance study of Morinda citrifolia and provides material basis and scientific basis for cold-resistant breeding of Morinda citrifolia.This study has important theoretical and practical significance.The main findings of this study are as follows:1.The results of natural chilling experiments in field tries showed that the five WTla,WTlb,WT2,WT3 and WT4 all had cold resistance,and their natural cold resistance was WTla>WT3>WT2>WTlb>WT4.2.Study on the cold resistance physiology of the germplasm resources of Morinda(1)Under low temperature stress,stress responses were observed in the MDA contents of 5 Morinda citrifolia germplasms,which first decreased and then increased,and the rising trend continued with the increase of treatment time.The MDA content of each germplasm showed significant difference(p<0.01).(2)Under low temperature stress,the relative electrical conductivities of the five Morinda citrifolia seedlings showed an upward trend,and the increase was related to the treatment time.In addition to WT2 and WTlb,the relative conductivity did not reach a significant level(P>0.05),and the rest showed a significant level(p<0.05).(3)The soluble sugar content of the five Morinda citrifolia seedlings showed an upward trend under low temperature stress.The soluble sugar content of the five germplasms increased sharply at the first day of treatment,except for a slight decrease in the content of WT3 and WT4 at the 2nd day.In order to increase continuously,the soluble sugar content of the five germplasms continued to increase after 4 days.The soluble sugar content of all kinds showed significant difference(p<0.05).(4)Under low temperature stress,the free proline content,POD activity,and SOD activity of the five Morinda cirrhosa germplasms all showed stress response,and the free proline content,POD activity,and SOD activity of the five germplasms were present at the 4th day after treatment.Obvious upward trend.Except for WT2 and WT4,the proline content was not significant(P>0.05),but the rest showed a significant level(p<0.05).Except for WT2 and WTlb,POD activity did not reach a significant level(P>0.05),and the rest showed a significant level(p<0.05).The activity of various SOD showed significant difference(p<0.05).The results of a comprehensive experiment show that the critical treatment time for stress response of physiological and biochemical indicators of Morinda citrifolia under low temperature stress were 4-6 days.(5)The membership function analysis results showed that the order of cold resistance of five germplasms was:WTla>WT3>WT2>WT1b>WT4.(6)The correlation analysis of the membership function of each cold-resistance physiological index showed that the relative electrical conductivity was the most relevant to the cold resistance,and the absolute value of the correlation coefficient was 0.926;the MDA content and the POD activity were related to the cold-resistance,followed by the absolute value of the correlation coefficient.They were 0.744 and 0.738,respectively;the absolute value of the correlation coefficient of soluble sugar content was 0.540;the absolute value of the correlation coefficient of proline content was 0.498;the absolute value of the correlation coefficient of SOD activity was the smallest,only 0.014.Relative electrical conductivity,MDA content and POD activity can be used as a reference index for evaluation of cold resistance of Morinda citrifolia.3.Study on the transcriptional study of Morinda citrifolia.(1)Functional annotation data analysis results showed that:NR function annotations 80,154 Unigene accounted for 68.50%;NT functional notes 54,683 Unigene accounted for 46.73%;SwissProt functional notes 52,33 Unigene accounted for 44.55%;KOG functional notes 62,173 Unigene accounted for 53.13%;KEGG Functional annotation 60,518 Unigene accounted for 51.72%;GO functional annotation 24,032 Unigene accounted for 20.54%;InterPro functional annotation 65,742 Unigene accounted for 56.18%.Transdecoder detected 91,348 CDSs,detected 25,250 SSRs in 20,325 Unigenes,and predicted 2,279 Unigenes that encode transcription factors.(2)CDS predictions showed a CDS number of 91,348,a total length of 82,275,939,a maximum length of 16,329,a minimum length of 297,and a base G and C ratio of 43.10%.The length of CDS is mainly concentrated between 200-2000,there are 84,992(93.04%),and 1774(1.94%)are more than 3000.(3)The results of differentially expressed genes showed that the number of DEGs up-regulated in Wla vs.CWTla germplasm was 10,890,the number of down-regulated DEGs was 11,451;Wla the number of DEGs up-regulated in WT1a germplasm was 362,and the number of down-regulated DEGs was 471;WT1a vs.CWTla germplasm.The number of up-regulated DEGs was 14,072,and the number of deregulated DEGs was 13,914.(4)The cold resistant genes of Morinda citrifolia are mainly concentrated in the Global and overview maps of metabolic pathways.(5)The main pathways related to cold resistance may be phytohormone signal transduction,glucose metabolism,and three carboxylic acid cycle.The difference genes mainly include phosphatase phosphatase,beta glucosidase,CTD nuclear envelope phosphatase,Peptide-O-fucosyltransferase,Protein TC075-3,acetyl coenzyme A,Auxin-responsive protein IAA8,Indole-3-acetic acid-amido synthetase GH3 and LSE0432 auxin response protein may be related to cold resistance of Morinda citrifolia. |
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