荧光假单胞菌Tn5诱变菌株防治小麦全蚀病的初步研究

 利用生物技术(转座子Tn5诱变)对荧光假单胞菌进行遗传改良获得对小麦全蚀病有更好防治效果的基因工程菌株。将大肠杆菌S17-1中psup2021值粒上的转座子Tn5转移到荧光假单胞菌CN12菌系的基因组内获得5100个Tn5突变体,转化频率为1.2×10^-7。与自然菌系CN12比较,7个突变体对全蚀病菌的离体拮抗作用提高到160-250%,其中3个突变体对温室苗期全蚀病防治效果也显著提高(p=0.01)。初步研究证明:(1)荧光假单胞菌中可能存在两类功能不同的拮抗作用基因(暂称为抗生基因和调控基因);(2)在目前抗病基因缺乏或难于应用的情况下,利用微生物或其有用基因达到防病增产的目的可能是一条有希望的途径。

GENETICALLY IMPROVED PSEUDOMONADS USED IN BIOCONTROL OF TAKE-ALL

By using molecular biological techniques (transposon Tn5 mutagenesis) it was demonstrated that genetically improved pseudomonad cultures were more suppressive to take-all disease of wheat.In matings between Escherichia coli S17-1 containing the suicide plasmid vector pSUP2021 and Pseudomonas fluorescens CN12, 5100 Tn5-induced mutants were obtained at a freqency of 1.2×10^-7 per recipient CFU.Frequency of mutation to auxotrophs was 0.8% Seven mutants (0.14%) consistently resulted in increased antibiosis (160-250% (of strain CN12) against Gaeumannomyces graminis var.tritici on PDA plates.In greenhouse pot tests for biocontrol,three mutants (727, 1533 and 2942) to increased antibiosis also exhibited significantly increased ability to control take-all,including disease severity, plant height and dry weight of wheat tops, as compared with strain CN12.A possible explanation of the results was given that mutation to increased antibiosis and suppression could result from Tn5 insertional inactivation of the regulatory gene coding for an inhibitor of antibiosis and/or suppression.