Tomato Mutation Genetic Analysis And Preliminary Study On Resistance Mechanism To Late Blight

Late blight, caused by the oomycete pathogen Phytophthora infestans（Mont.）de Bary has a serious disease of Solanaceous crop tomato in the world,especially under protected cultivation conditions. At present, a number of tomatoresistant genes (Ph-1, Ph-2, Ph-3, Ph-4and Ph-5) from different wild species oftomato have been overcomed and resistance loss beceuse the high evolutionary andfrequent variation of Phytophthora infestans. Therefore it’s important to explore themechanism of anti-disease gene and understanding of tomato late blight interactionwith regulatory mechanisms if we want to cultivate lasting disease-resistant varietiesof tomatoes.The interactions of late blight resistant gene R3a from potato and Avr3a fromPhytophthora infestans suit to the gene-for-gene model. As autotetraploid plants andhighly complex genomes, potato aren’t suitable for experimental material. The studyestablished the system named MM-R3a-Avr3a which containing R3a gene and Avr3agene induced by DEX. It provided research basis for key gene cloning of resistancepathway, by constructing mutant library, screening live mutant, molecularidentificating and genetic analyzing the mutant.1. Transgenic tomato MM-R3a-Avr3a treated by EMS mutagenesis to builtmutant library, Ultimately screening of the1057and2308HR response blocking ofmutant families treated by DEX; RT-PCR the results showed that key genes mutantcause R3a-Avr3a interaction signal recognition pathway blocked, because of R3a andAvr3a gene in mutant tomato can normal expression; Phytophthora infestansinoculation show that the mutant tomato resistance loss of the late blight.2. Two pure transgenic tomato mutant families respectively with tomatoMoneymaker and transgenic tomato MM-R3a-Avr3a hybridization. According to theresult of genetic analysis, F2generation of HR and HR reaction separation ratio of3:1,determine the mutant tomato1057and2308single gene mutation is invisible.3. From the analyses on1057and2308famlies by the active oxygen way,mutants treated by DEX generated O2-and acculumated H2O2, but HR reaction didn’thappen, which expressed that the pathway of original O2-generation and H2O2 acculumation in mutants didn’t been cut off. The results of qRT-PCR and antioxidantenzyme activity showed that mutants (POD、CAT、APX) treated by DEX and controlgroups both exhibited differences. Antioxidant gene (SOD、CAT、PPO) in mutantsdidn’t expressed up-regulation, which proved that there existed a close relationshipbetween mutant gene and Antioxidant pathway.4. The results of ethylene production analyses showed that ethylene productionin mutants was restrained. From the analysis of some important genes in the ET、JAand SA resistance pathway, transgenic tomato MM-R3a-Avr3a compared withMoneymaker, EIN2、COI1、JAR1、EDS1、NIM1、PR1genes expressions showedvarious degrees of increase after DEX treatment which indicated these genesparticipated in R3a-Avr3a gene interaction signal transduction. Mutants gene exceptJAR1and NIM1overexpressed, the others were inhibited. Therefore mutant genes ofmutants located up the EIN2、COI1、EDS1、NIM1、PR1, and they took part in theoriginal singal transduction of R3a-Avr3a mutation.