Cloning Of The Genes In Chinese White Pear Cultivars Resistant To Valsa Canker And Investigation Of Its Resistance Mechanism

China is the largest country of pear production in the world,but pear trees have been suffering from valsa canker,causing great economic losses.The disease is a kind of weak pathogenic diseases caused by fungus V.mali var.pyri that mainly infect the trunk,branch and shoot,and cause decay of the weak tree bark and decline of fruit yield and quality.The onset of symptoms and the infection characteristics at different areas in China are basically similar,mainly presented as canker type and twig blight.Currently the control method is mainly chemical application;the potential way for the control of the disease rely on the cloning of related genes resistant to Valsa canker or breeding of resistance cultivars.The article study the resistance mechanism of valsa canker at the molecular level,screening of resistant varieties and susceptible varieties of ‘qiubai' and ‘chili'.The pilot samples were treated with roting pathogen inoculation for Illumina HiseqTM2000 sequencing.And through the real-time fluorescence quantitative?qRT-PCR?technology,we verified the result of the transcriptome.Significant disease resistance genes screened were taken for total length cloning.Hydrogen peroxide kit was used to test endogenous H₂O₂ levels of ‘qiubia' and ‘chili' branches after different treatment.With high performance liquid chromatography,we had qualitative and quantitative analysis on phenols of each ‘qiubai' and ‘chili' branch cadres.By enzyme linked immunosorbent assay,we got the content of endogenous SA and JA in ‘qiubai'and ‘chili' branches.The results show that :?1?Trough dormant branches burn method,we filter the inoculated bacteria resistant germplasm resources,that is in 8 white pear varieties,disease resistant varieties ‘qiubai' and susceptible cultivar 'chili' has been screened.?2?By Illumina HiseqTM2000 sequencing for different samples,the accuracy of quantitative fluorescence technology transcription has verified the accuracy of transcriptome results.We have screened some significant difference genes and selected two differentially expressed genes forcloned and fluorescence quantitative PCR analysis.?3?With high performance liquid chromatography determination on the phenolic compounds of different treatment,we found that most of the content of phenolic compounds is arbutin,chlorogenic acid and epicatechin.Using different exogenous we found: ' qiubai' after exogenous SA treatment its internal arbutin,chlorogenic acid and catechin change is on the decline;after exogenous JA treatment its internal arbutin and chlorogenic acid content changes are falling before they rise;after inoculation of rot disease its internal germs arbutin and table catechins content showed a trend of rising all the time.'chili' arbutin content changes,falling and rising;chlorogenic acid rot in vaccination and JA rise after falling after;epicatechin present different change trend after different treatment.?4?The study has showed the changes of the endogenous H₂O₂ level.The H₂O₂ level has rise after the treatment of exogenous SA,while rhe changes in H₂O₂ level of'qiubai' and 'chili' with rot disease bacteria inoculation and exogenous JA method are instead.?5?Treated with exogenous JA,SA,results showed that the poor disease resistance 'chili' with exogenous stimulation can cause the increased of SA content and the decrease of endogenous JA content,and two of them showed antagonistic effect.As 'qiubai' got exogenous stimulation,the contents of endogenous JA will fall;and the contents of endogenous SA may decline after treated with exogenous SA.The research results show that,the endogenous SA and JA may be involved in the resistance of rot disease that affected by pear germplasm resources.