Analysis Of Inducement Of Abnormal Mosaic Phenomenon In Loropetalum Chinense Var.rubrum

Loropetalum chinense var.rubrum is a precious garden plant with both flower and leaf viewing functions.Leaf color is one of the important economic characters that determine its ornamental value.In garden application and nursery breeding,many Loropetalum chinense var.rubrum have been found to have abnormal mosaic symptoms,but it has not been studied in detail at home and abroad.Therefore,in this study,abnormal mosaic of Loropetalum chinense var.rubrum plants was as the research object to preliminary explore the causes of abnormal mosaic phenomenon from the investigation,nutritional deficiency diagnosis,virus detection and transcriptome sequencing analysis and other methods.The main research results were as follows:1.Through the investigation of the abnormal mosaic phenomenon of Loropetalum chinense var.rubrum,it was found that the incidence of abnormal red and yellow mosaic leaves was the highest,which was 42.52%.And the abnormal mosaic phenomenon were easy to occur in the residential green space,the form of shrub ball,the young leaves outside the tree crown,the shade,the pruning,the incidence was 54.05%,37.64%,83.55%,48.68%,94.32%,respectively.However,after further observation,no fungal and bacterial diseases,and few pests were found.The factors of pests,fungal and bacterial diseases were preliminarily excluded.The diagnosis of nutritional deficiency showed that the symptoms of mosaic were slightly improved but still existed,and the physiological disease factors were preliminarily excluded.2.The abnormal mosaic of Loropetalum chinense var.rubrum were detected for plant virus.In the biological test,pepper,tobacco and cucumber showed mild virus symptoms,petunia did not respond,tomato showed virus disease symptoms such as mosaic,vein cleaning,yellow,small leaves,leaf margin shrinkage,etc,and the control group did not get sick.Suspected linear and spherical virions of Loropetalum chinense var.rubrum were observed by electron microscopy.The suspected Chrysanthemum B virus and Cucumber mosaic virus were detected by enzyme-linked immunoassay,but the results were negative.By RT-PCR and blast analysis were performed on 6 common mosaic viruses and 4 viruses obtained from high-throughput sequencing analysis,and no nucleic acid sequences with high homology were found.In conclusion,the abnormal mosaic symptoms of Loropetalum chinense var.rubrum may be caused by viruses,but the specific virus species cannot be detected,it may be due to low amount of viruses contained in the sample itself,poor primer specificity,deviation of sequencing results,or limited detection range of viruses and other reasons.As a result,the specific type of virus could not be identified,which needs further research and identification.3.By transcriptome sequencing analysis,39334524 clean reads and 53945087 clean reads were obtained from abnormal mosaic leaves and normal leaves of Loropetalum chinense var.rubrum,respectively.The number of annotated transcripts in KOG,KEGG,NR,GO and Swiss-Prot databases were 22630,27412,62825,43110 and 51460,respectively.A total of 133 KEGG pathway enrichment pathways were annotated,including 4 leaf color related enrichment pathways.Further analysis showed that POR and HEMA,the key structural genes in porphyrin and chlorophyll metabolism were down-regulated.In the differential expressed analysis results,a total of 635 transcription factors were screened,belonging to 49 transcription factor families.The most significant enrichment was the MYB transcription factor family,included 86 differential expressed transcription factor,most of them were down-regulated.4.Three differential expressed genes POR、HEMA、MYB that may play an important role in the abnormal mosaic of Loropetalum chinense var.rubrum were screened for real-time quantitative PCR,and the verification results were consistent with the results of transcriptome sequencing.The results showed that these genes may be the key genes leading to the abnormal mosaic symptoms of Loropetalum chinense var.rubrum,the specific molecular mechanism needs to be further studied.