Isolation of Fusarium fujikuroi antagonistic bacteria and cloning of its phenazine carboxylic acid genes

Bakanae disease caused by Fusarium fujikuroi is very important in rice. Pseudomonas fluorescens produces a broad-spectrum antibiotic phenazine-carboxylic acid (PCA), which is active against a variety of fungal root pathogens. In this study contaminated rice samples were collected from infected farms of Guilan. 238 bacteria were isolated from rhizosphere and the antagonistic ability of 12 of them was demonstrated with two culture method. Eight of these isolates were identified as P. fluorescens. The effects of volatile metabolites produced by antagonistic P. fluorescens found in the isolates inhibited growth of F. fujikuroi in vitro. Culture filtrate and antibiotics from these isolates inhibited growth of the pathogen. Two genes from seven gene locus of phenazine were cloned in Escherichia coli DH5

Isolation and identification of bacterial glum blotch and leaf blight on wheat (Triticum aestivum L.) in Iran

Basal glume blotch and leaf blight of wheat caused by Pseudomonas syringae pv. atrofaciens and P. syringae pv. syringae respectively are the bacterial diseases of wheat in Iran. The disease causes damage on wheat which leads to lots of yield and crop losses in the host plants. During the spring and summer of 2005-2006 different wheat fields in Guilan province (Roodsar, Langrud, Rostamabad, loshan, and Roodbar) were surveyed. Samples were collected from infected wheats with glumes blotch and leafblight. Infected tissues were washed with sterile distilled water and crushed in peptone water. Then 50 ìl of the extract were cultured on King’s B and NA media containing cyclohexamide (50 ìg/ml). After 48 to 72 h, bacterial colonies were selected and purified. On the basis of morphological, physiological and biochemical characteristics, pathogenicity and PCR with specific primers, the isolated were placed in two groups. The first group consists of 20 isolates that caused leaf blight, identified as P. syringae pv.Syringae, while the second group is made up of 18 isolates that caused basal glumes blotch identified as P. syringae pv. atrofaciens. This is the first report of the existence of P. syringae pv. atrofaciens on wheat in Iran