The Functional Study Of Endopolygalacturonase Genes In Valsa Mali

Apple Valsa canker, caused by Valsa mali, is one of the most important stem diseases ofapple trees in China. It can causing destructive rot in phloem and xylem of apple tree, andeven tree death, has been the key objects of prevention and treatment in apple production.Unfortunately, no actively, efficiently and purposefully control method has been developedfor this serious disease so far because the pathogenesis is not clear. It is reported that Valsamali secrets a large number of pectinase during infection which caused pectin degradationand tissue rot. There into, the endo-polygalacturonase may plays an important role inpathogenicity. Thus, to detect the function of pectinase during the fungal infection, threeendo-polygalacturonase genes Vmpg-4、Vmpg-5and Vmpg-6from the V. mali were knockedout based on the PEG mediated transformation. Finally, we got three results.1. Based ondouble-joint PCR, the gene knockout cassetes of three endo-polygalacturonase genes,Vmpg-4,Vmpg-5and Vmpg-6were constructed.2. Through PEG mediated transformation,900,237and106candidate transformants ofVmpg-4, Vmpg-5and Vmpg-6were obtained respectively. Then13,0and1were provedrespectively by PCR. However, only4mutants of gene Vmpg-4deletion mutant wereobtained after southern blot verification.3. In order to known the phenotype and pathogenicity of Vmpg-4, bioassay on thedetached leaves (Fu ji) was performed. Results showed that there were no significantdifference between Vmpg-4and wild type in growth rate, colours of colony, emerging timeand quantity of pycnidia and the pathogenicity. It suggests that endo-polygalacturonasegene Vmpg-4might not play a key role in phenotype and pathogencity. Otherwise, theendo-polygalacturonase genes indicate redundancy.