青枯雷尔氏菌无致病力突变菌株的构建及其防效评价模型分析

 利用青枯雷尔氏菌(Ralstonia solanacearum)无致病力菌株防治番茄青枯病具有很好的应用潜力。作者通过分离筛选自然弱毒株、⁶⁰Co辐射诱变和EZ-Tn5插入诱变,分别获得3、12和40株青枯雷尔氏菌无致病力突变菌株。经盆栽番茄苗致病性检测,15 d后均未发病,证实均为无致病力青枯雷尔氏菌。进一步对番茄青枯病的防治试验表明,从番茄青枯病发病田块分离的无致病力突变菌株FJAT1458的防治效果最好,防效达100%。该菌株能定殖番茄植株根系土壤、根部和茎部,定殖数量均表现为“先增后减”的趋势,并且接种浓度越大、苗龄越小,定殖数量越大。从构建的防效模型可以看出,不同接种浓度条件下,植株发病率随时间变化符合的回归方程不同,相关系数R值也不同,接种浓度越大,R值越小。本研究获得的青枯雷尔氏菌无致病力突变菌株FJAT1458对番茄青枯病具有很好的防病效果。

Construction of Ralstonia solanacearum avirulent mutants and evaluation model of their control efficacy against tomato bacterial wilt disease

Avirulent Ralstonia solanacearum has showed a good potential on control bacterial wilt disease of tomato. In this study, 3, 12 and 40 avirulent mutants of R. solanacearum were constructed by using spontaneous mutagenesis, ⁶⁰Co-radiated mutagenesis and EZ-Tn5 transponson mutagenesis, respectively. Pathogenicities of these 55 mutants were detected with bioassay test using potted tomato in the greenhouse. None of these mutants caused tomato wilting at 15^th d after inoculation, which meant that they were all avirulent R. solanacearum. Then, the 55 mutants were used to control tomato bacterial wilt and the control efficiencies were compared. The results showed that strain FJAT1458 isolated from tomato plant was the most effective with the control effect of 100%. It was also found that strain FJAT1458 could colonize in rhizospheric soil, root and stem of tomato plant. The colonizing density of FJAT1458 showed a tendency of ′increasing at the beginning and decreasing afterward’ during 1-25 d after inoculation. Meanwhile, higher inoculated concentration and younger seedling age resulted in more colony amount of FJAT1458 in plant. A regression model of control efficiency of the biocontrol agent against tomato bacterial wilt was constructed. When the inoculated concentration of FJAT1458 was bigger, the value of R was less. Therefore, the avirulent mutant FJAT1458 obtained is possessed of good control effect on tomato bacterial wilt.