Biological control for crown and root rot disease of tomato caused by Drechslera halodes in Iraq

Abstract

Isolation from infected Tomato's plants has demonstrated the presence of the phytopathogenic fungus Drechslera halodes (Dh) the causal agent of leaf spot, crown and root rot disease, samples were collected from three provinces in the middle and south of Iraq, Dh was predominant while appeared in 83.33% of the samples with frequency of 50.25%. Results of pathogenicity test under greenhouse conditions indicated that all the isolates of Dh were pathogenic to tomato plants, the isolate Kkd-6 showed highly pathogenicity effect. Four isolates of beneficial free-living soil bacteria isolated from healthy tomato's rhizosphere of Bacillus subtilis (Wb-12), B. subtilis (Kb-9), Enterococcus columbae (Bb-8) and Pseudomonas putida (Kb-18), were exhibited 100% antagonism efficiency against the pathogen on the potato dextrose agar medium (PDA) in vitro. Under greenhouse conditions all the biocontrol agents were reduced significantly the percentage of disease incidence to 5-10% and severity of shoot and root system to 5.00-8.33%, 2.14-7.14% respectively compared to fungal treatments control which exhibited 100% disease incidence and severity of shoot and root system of 90.00%, 93.57% respectively. All the biocontrol agents promoted plant growth. This is first report of Drechslera leaf spot, crown and root rot disease of tomato in Iraq.