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Molecular Plant Pathology

Genetics of Antibiosis in Bacterial Strains Suppressive to Take-All. Alan R. Poplawsky, Postdoctoral research associate, Department of Plant Pathology, University of Wisconsin-Madison; Yufa F. Peng(2), and Albert H. Ellingboe(3). (2)Former visiting scientist, Department of Plant Pathology, University of Wisconsin-Madison, Present address: Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, P.R.C. (3)Professor, Department of Plant Pathology, University of Wisconsin-Madison. Phytopathology 78:426-432. Accepted for publication 12 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-426.

We initiated a genetic analysis of the interaction between the fungal pathogen, Gaeumannomyces graminis var. tritici and bacterial strains involved in suppression of the take-all disease. Tn5-induced mutants of three bacterial strains (Pseudomonas fluorescens NRRL B-15133, NRRL B-15135, and strain 111) that inhibit the growth of the pathogen on agar media (antibiosis) were obtained. Mutants for auxotrophy (0.67%), increased antibiosis (0.83%), loss of antibiosis (0.38%), and loss of fluorescence on King’s Medium B (NRRL B-15135 only, 0.53%) were obtained. When 48 mutants affected in antibiosis were analyzed by Southern blot hybridization, 45 contained insertions in single EcoR1 fragments. From these results it was estimated that mutation at six to 10 different loci resulted in a loss of antibiosis. The data suggest that with each strain insertions of at least one half of the prototrophic, antibiosis-negative mutants may be clustered in one or two regions of the bacterial genome. Genomic cosmid clone banks were prepared from two strains (B10 and 121) that did not inhibit the growth of the pathogen on agar media, and transferred to strain NRRL B-15135. One 121 cosmid clone inhibited the expression of antibiosis in this strain, as well as two other strains. Thus, two types of bacterial genes important for the in vitro interaction with the pathogen were identified in this study.

Additional keywords: biocontrol.