Germplasm Identification And Gene Mapping Of Mustard (Brassica Juncea) Resistance To Turnip Mosaic Virus

Mustard(Brassica juncea) is an economically important vegetable crop in the world with the wide planting area. According to their edible organs, Mustards can be devided into root mustard, stem mustard, leaf mustard, sprouts mustard, seed mustard. The virus disease is the main disease affecting the production of mustard. Turnip mosaic virus (TuMV) is the main pathogen causing virus disease. Plant displays symptoms such as:mosaic patterns, vein clearing, stunting, and even necrosis after TuMV infection. Recently, TuMV substantially decrease the yield of mustard since there is hardly any resistant cultivar. In this thesis, we would like to identification TuMV-resistance gene using36mustard varieties as material. The main results were shown as follows:1Resistance identification of36Brassica materials36Brassica materials were inoculated with TuMV isolate, then symptoms investigation, TuMV-CP gene expression analysis and ELISA test were performed. Finally,6mustard materials were found to be TuMV-resistant(R).2Genetic analysis of TuMV-resistance geneThe F2population was deduced from the cross of the TuMV resistance lines VC029and susceptible lines STZ. VC029(10individuals), STZ (10individuals), F1(20individuals) and F2(226individuals) were inoculated with TuMV isolate. All VC029line plants were found to be resistant to TuMV, while both STZ line and F1progeny were susceptible. The segregation ratio of the TuMV responses of the F2generation (55resistant and171susceptible) is near1:3, indicating that TuMV-resistance phenotype is controlled by a single recessive allele in mustard.3TuMV-resistance gene mappingTo locate the TuMV-resistance gene, F2population were used to establish the susceptible bulk and the resistant bulk for re-sequencing.In the susceptible bulk, the sequencing depth is38X and the coverage on the genome is97.80%.In the resistant bulk, the sequencing depth is34X and the coverage on the genome is96.32%. Association analysis of genome sequences and resistance phenotype provide us145 DNA regions.