A GENOMIC REGION FROM PSEUDOMONAS-FLUORESCENS PF-5 REQUIRED FOR PYRROLNITRIN PRODUCTION AND INHIBITION OF PYRENOPHORA-TRITICI-REPENTIS IN WHEAT-STRAW

Pseudomonas fluorescens strain Pf-5, which produces many antifungal metabolites including pyrrolnitrin, inhibited mycelial growth of Pyrenophora tritici-repentis in agar culture and suppressed ascocarp formation by the fungus on axenically infested wheat straw kept moist during incubation. Purified pyrrolnitrin was similarly inhibitory. A Tn5 mutant of Pf-5 that did not produce detectable levels of pyrrolnitrin did not inhibit P. tritici-repentis on a culture medium or on wheat straw. A genomic region of Pf-5 was cloned that restored the pyrrolnitrin-deficient Tn5 mutant to pyrrolnitrin production and antagonism to P. tritici-repentis in culture. Pf-5 did not persist or suppress P. tritici-repentis on naturally infested wheat straw incubated under simulated field conditions of fluctuating moist and dry periods.