Analysis Of Copper Resistance In Acidovorax Citrulli

Bacterial fruit blotch of melons and watermelons, caused by Acidovorax citrulli, is a seed bornequarantine devastating disease worldwide. It has agreat genetic diversity, and can be mainly typed intotwo groups: strains in groupⅠwere mainly isolated from melons and pumpkins; strains in groupⅡwere mainly isolated from watermelons. Since the diease was firstly reported in1998, it spreaded fast inChina to cause serious damages to the plants of cucurbits, and has been a hard nut to crack.In this study, the143strains of A. citrulli from two subgroups were Cultivated for ten generations,and tested for copper sulfate sensitivity, using streak plate method. According to the result, we analysedthe differences of copper sulfate sensitivity between groups and hosts, and tested the control efficiencyof copper sulfate to the two groups strains. Two mutants were generated in the background of twostrains Pslb3, Aac-5, using the method of triparental cross. Copper sulfate sensitivity, pathogenicity,motility were tested on mutans, wild type and complementary strain to explore the difference of coppersulfate sensitivity between two groups on gene level and the function of gene0034.(1) only one strain was sensitive to copper sulfate under the concentration of300μg/mL. All strainswere sensitive under the concentration of750μg/mL. The same sensitivity of subcultured strains andoriginal strains indicate that A. citrulli has stable resistant ability to copper. Strains from groupⅠandmelons has better copper resistance than strains from groupⅡand watermelons, under the concentrationof500μg/mL, all groupⅡ strains are sensitive, and98%groupⅠ strains are not sensitive,32%strainsfrom watermelon can grow, while only8%strains from melon can not grow. control efficiency researchindicate that copper sulfate has a better effect to high sensitivity strains than low sensitivity strains andthere is a big difference of pathogenicity between strains.(2) Mutant strains Pslb3△0034、Aac-5△0034can not grow on the plate under the concentration of100μg/mL after3days, and can shaped much less colony than wildtype strains after10days. Twomutants are both sensitive under the concentration of150μg/mL. It indicates that gene0034plays a bigrole in the different copper resistance between two groups. there is no big difference of pathogenicity,motility, growth rate, EPS, hypersensitivity, biofilm formation between mutans and wildtype strains.