Study On Pathogenesis Of Rubber Witches’ Broom Disease Based On Transcriptome Level

Natural rubber produced by Hevea brasiliensis(will.Ex A.Juss.)Muell.Arg is an important industrial raw material and strategic material.At present,China’s planting area is more than 17 million mu,mainly distributed in Yunnan,Hainan and Guangdong province,with an annual output of more than 800000 tons.The planting area and rubber production are ranked fourth in the world.Brown skin disease of rubber tree is an important cutting surface disease in the world.The average loss of dry gum caused by brown skin disease is more than 10%,and the economic loss is extremely huge.Rubber tree witches’ broom is an infectious disease caused by MLO and RLO.The occurrence of rubber tree witches’ broom is closely related to the occurrence of rubber tree brown skin disease.The propagation of the shoots of rubber tree witches’ broom in nursery is one of the important primary infection sources of field brown skin disease.In this study,the branches and healthy branches of rubber witches’ broom were used as materials.The paraffin section method was used to observe and compare the structural differences of the stems and leaves of the diseased and healthy branches,and the correlation between the structural changes of diseased tissues and their external morphology was analyzed.At the same time,based on the transcriptome sequencing,the genetic differences between diseased and healthy rubber were compared,and the biological functions of the different genes were analyzed In order to further explore the causes of the disease at the molecular level.Based on the analysis of the transcriptome of rubber clumps,the correlation between rubber clumps and red sandalwood clumps in India was preliminarily explored by using the transcriptome sequencing technology.The results are as follows:1.The results of light microscope anatomical observation by paraffin section method showed that,compared with healthy rubber branches and stems,the apical buds of rubber branches and stems with witches’ broom became weak and small,the lateral buds differentiated and germinated ahead of time,resulting in clusters,the cambium and periderm became thinner,the stone cells or stone cell clusters did not exist outside the primary phloem fibers,the cells near the cambium arranged irregularly and lignified Compared with the healthy leaves,the number of burr on the back of the rubber leaves with witches’ broom decreased,the palisade tissue became thinner,the sponge tissue became thicker and the cells arranged irregularly.2.A total of 5928 genes were differentially expressed in symptomatic and non symptomatic samples and 4370 genes were differentially expressed in healthy samples.In order to explain the molecular mechanism of rubber witches’ broom disease more accurately,the differential genes screened were enriched with go and KEGG,and it was found that the symptoms of witches’ broom disease were mainly regulated by plant hormone signal transduction pathway and metabolic pathway.Plant hormones play an important role in the regulation of plant growth.Many key genes in plant hormone signal transduction pathway are significantly differentially expressed in diseased rubber,which may play an extremely important role in the regulation of rubber clump phenomenon.Metabolic pathways provide nutrients for normal growth and development of plants,and play an important role in many defense responses.3.12 key DEGs were screened and identified by QRT PCR.It was found that the difference multiple of gene expression amount was almost the same as that of transcriptome data,which proved that the key genes of differential expression obtained by transcriptome sequencing in this study were reliable.4.On the basis of the rubber transcriptome,the samples of rubber witches’ broom and Indian rosewood witches’ broom were analyzed with no reference transcriptome.