Determination of in vitro Biocontrol Potentials of Antagonist Bacterial Isolates against Walnut Blight Disease Agent Xanthomonas arboricola pv. juglandis

Abstract

Walnut blight disease, caused by Xanthomonas arboricola pv. juglandis (Xaj), is one of the most important and common bacterial disease which effects production of walnut (Juglans regia L.) plants. The bacterial disease is led to economic losses significantly in juglans growth fields of Turkey. Typical symptoms occur on all succulent tissues including shoots, leaves, rachis, petioles, buds, female flowers, catkins and nuts. Infection begin as translucent water-soaked areas which develop into brown to blackish greasy necrotic areas. Lesions, which are often surrounded by a yellow-green halo, are initially circular but often expand into angular spots. Management of the pathogen is suggested the cultural methods and using copper compounds. Recently, controlling bacterial diseases the eco-friendly biological control studies are increased to control bacterial diseases. In this study, isolation and identification of disease agent Xaj from infected plants and antagonistic potentials of candidate bacterial antagonist biological control agent were investigated for their ability to suppress bacterial growth in vitro conditions. Bacterial disease agents were isolated and identified according to morphological and biochemical methods. Using selective nutrient media, total of 109 candidate antagonist bacterial isolates were isolated from different healthy walnut plant leaves and investigated for their ability to suppress bacterial growth in vitro conditions by dual culture test. From this test, eighty-one bacterial isolates were found to produce inhibition zones a varying size (range of 3.44-30.00 mm). Among the 80 isolates, thirty-seven isolates were able to suppress the bacterial growth completely. According to preliminary results of the significant suppression in the bacterial growth caused by antagonist bacteria, bacterial isolates could be used as possible biocontrol agent against walnut bacterial blight disease. Further studies should be conducted on identification and determination of mode of actions and in vivo activities of the most efficient bacterial isolates against disease agent. © Bu çalışma Tekirdağ Namık Kemal Üniversitesi tarafından.