Suppression of Septoria tritici Blotch and Leaf Rust of Wheat by Recombinant Cyanide-Producing Strains of Pseudomonas putida. Moshe A Flaishman. Department of Botany, The George S. Wise Faculty of Life Science, Tel-Aviv University, Tel-Aviv 69978, Israel. Zahir Eyal (1), Aviah Zilberstein(1), Christophe Voisard(2), and Dieter Haas (2). (1) Department of Botany, The George S. Wise Faculty of Life Science, Tel-Aviv University, Tel-Aviv 69978, Israel, (2) Department of Microbiology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland. MPMI 9:642-645. Accepted 13 June 1996. Copy right 1996 The American Phytopathological Society.

Pseudomonas putida strain BK8661, which produces si-derophore(s), antibiotic(s), and low levels of hydrogen cyanide (HCN), suppresses growth of Septoria tritici and Puccinia recondita f. sp. tritici in vitro and on wheat leaves. Pleiotropic mutants of strain BK8661 deficient in sidero- phore and antibiotic synthesis were significantly less effective in suppressing symptoms than was the wild type. HCN overproducing derivatives of the pleiotropic mutants were constructed by the integration of the hcnABC gene cluster from Pseudomons fluorescens CHAO. In (he absence of siderophore(s) and antibiotic(s), HCN production by the overproducing bacterial strains resulted in a small but statistically significant increase in the suppression of symptoms caused by 5. tritici and P. recondita f. sp. tritici on wheat seedling leaves.