| It is one of the important tasks for the development of natural rubber industry to implement the effective supply and quality improvement of natural rubber and give priority to the safety level of rubber used in key fields.Natural rubber is a strategic material for national security.More than 98% of the natural rubber in the world comes from Hevea brasiliensis.Red root disease of rubber trees is the most important root disease of rubber trees in China.At present,the lack of resistance of plant varieties in production and the unclear disease resistance mechanism limit the accurate implementation of prediction and prevention measures of this disease.In recent years,with the continuous development of high-throughput sequencing technology,more and more studies have been conducted to explore the driving factors of red root infection of Hevea rubica from the perspective of microecology.In this study,by analyzing the types of cell wall degrading enzymes that play a major role in the infection process of R.hevea and their infection process to the roots of B.hevea,the changes of cell wall related enzyme activities and related gene expression were studied to determine whether cell wall degrading enzymes are the main pathogenic biochemical factors of R.hevea and to identify the cell wall degrading enzymes that play a key role.It laid a theoretical foundation for the prevention and control of red root disease and breeding against red root disease in rubber trees.The main results are as follows:1.Sampled the roots of the infected rubber trees from the third team of the Experimental Field of Chinese Academy of Tropical Agricultural Sciences,I conducted fungal isolation and isolated a pathogenic fungus that determined the morphological characteristics and pathogenicity of the pathogenic fungi,and determined the r DNA-ITS sequence of the pathogenic bacteria for comparison and identification,so as to determine the pathogenic fungi causing the root disease of the rubber trees and eventually death.Ganoderma pseudoferreum is a related fungus of ganoderma genus.The outer layer cells of root epidermis were destroyed on the 3rd day after the tissue culture of Hevea sinensis infected the seedlings,and the epidermis cells were occupied by the bacteria on the 7th day.2.2.3,5-dinitrosalicylic acid(DNS)method and ultraviolet spectrophotometer were used to detect the changes of cell wall degrading enzyme activities during the infection of R.hevea.The effects of cell wall degrading enzymes on root damage and pathogenicity were analyzed by measuring the osmotic reducing sugar and relative electrical conductivity of the root of hevea rubber tree treated with the enzyme.Among the cell wall degrading enzymes detected,the activity of neutral xylanase was the highest,followed by β-glucosidase,and the activity of neutral protease,pectin methyl trans-cancelling enzyme and other enzymes was lower.Both single and mixed enzymes produced by R.rubberica could cause significant damage to root tissue and affect root vitality.3.The full-length sequence of cellulase Gp TR6079 was 1302 bp and encoded433 amino acids by RT-PCR.The probability of the presence of signal peptide in cellulase Gp TR6079 protein was 0.9945,and the position of signal peptide was between GAA and AS.The full-length sequence of β-glucosidase Gp TR894 was1563 bp,encoding 520 amino acids.The probability of the presence of signal peptide in β-glucosidase Gp TR894 protein was 0.9483,which was located between ARG and AY.The full length sequence of Gp TR1774 was 780 bp,encoding 259 amino acids.The relative expression levels of cellulase Gp TR6079,β-glucosidase Gp TR894 and xylanase Gp TR1774 were analyzed by q RT-PCR after the infection of Rhizoma rubosa with Hevea sinensis.The expression levels of cellulase Gp TR6079,β-glucosidase Gp TR894 and xylanase Gp TR1774 were firstly increased and then decreased after inoculation with B.hevea.The expression levels were significantly increased at the 3rd and 4th day of infection.4 d reached the highest level. |
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