Screening For Resistance To Sclerotinia Sclertiorum In Arabidops Mutants And Studies On The Expression Of Defense Genes Of Go-Transgenic Rapeseeds

The fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary distributes widely and infects more than 450 plant species worldwide. In China, this disease causes significant yield losses of various important crops,including oilseed rape, soybean, sunflower and Brassica vegetables.Oxalic acid (OA), a non-host-specific toxin, secreted by S.sclerotiorum, has been demonstrated to be a major phytotoxic and pathogenic factor. It is regretful that no germplasm resources in host plant species are found to be immune or effective to S. sclerotiorum.After methods of screening for resistance to Sclerotinia sclerotiorum in Arabidopsis mutants were established, a total of 51 600 mutant plants originated from estrogen-inducible activation tagging T-DNA insertion lines were screened. Of them, 5000 plants were screened using mycelial inoculation method and significant differences in development rate and size of lesions caused by S. sclertiorum were found between mutants. The rest mutants were screened by a two-step method, i.e. germinating seeds were treated with S.sclertiorum toxin oxalic acid and then survived plants were inoculated with S. sclerotiorum. Mutants capable of surviving on MS agar medium supplemented with 2 mmol/L oxalic acid and 17-β-estradiol (an activation mutation inducer) were PCR detected and the positive plants were identified by inoculation with mycelium 15 d after transferred into pots full of peat-based compost. Two Arabidopsis mutants were selected with significantly slower development and smaller size of lesions. The results indicated the two mutants were loss-of-function mutants.In addition , reverse-transcription PCR (RT-PCR) was used to study differential expression of defense genes in GO-transgenic rapeseed inoculated with S.sclerotiorum.The result showed that up-regulated expression of PR-1 in GO-transgenic rapeseed was distinct than in control.In the inoculated plants the expression of defense genes PDF1.2,NPR1,PR-1 were all higher than that in the uninoculated control plants .One possible explanation was that oilseed rape achieved defence after GO gene introduced into them and the defense reaction was activated by the S.sclerotiorum invasion. However,the reason for this will be...