Construction Of Mutants Library Of Acidovorax Citrulli And Screening Of Mutants With Cellulase Activity

In this experiment transposon Tn5was transferred into strain A13of Acidovoraxcitrulli,and4136cloning strains were obtained.Through further screening withmotility, activity of extracellular and cellulase to the colons,a strain that lost thecellulase activity was found from the colons and named as mutant strain13-30.Assaying the biological characteristics of the mutant strain13-30with growth,motility, pathogenicity and stability, the mutant strain13-30was found not only had agood stability, but had the similar growth characteristic and motility with wild strainA13. However, the mutant strain13-30had lost the pathogenicity ability towatermelon seedlings.The mutant strain13-30was used to prevent and control the disease of bacterialfruit blotch of watermelon. The results showed that if the wild strain A13wasinoculated after3hours of inoculating the mutant strain13-30to the watermelonseedlings, there was a certain prevention effect in5days,then the disease index weredeveloping.If the wild strain A13was inoculated after6hours of inoculating themutant, there was a prevention effect of43.1%in7days,but in20days developed to32.5%.If after12,18,24and36hours of inoculating the mutant strain,the preventioneffect were76.1%,80.2%,75.2%and78.8%in7days respectively, even in20daysthe prevention effect still kept to65.3%-67.8%.