معرفی و ارزیابی قابلیت آنتاگونیستی باکتری Delftia acidovorans در برابر بیمارگر عامل آتشک سیب و گلابی و بلاست مرکبات

Fire Blight is one of the most dangerous diseases of pome fruits in many parts of the world. The main symptoms of the diseases include blossom blight, necrosis, blackening of petiole and necrosis and bending of twigs in a characteristic way forming the symptom known as "shepherd's crook". Citrus blast disease caused by Pseudomonas spp. is one of the most important citrus diseases in the northern citrus growing provinces of Iran due to the climate conditions which are conductive to its development significant damage in the form of twig and shoot dieback. In the present study one hundred isolates of epiphytic bacteria, were recovered from healthy-looking blossoms of pome fruits and tested for their ability to inhibit the growth of E. amylovora, the agent of fire blight and P. syringae pv. syringae and P. viridiflava the casual agents of citrus blast disease. The pathogenicity of these agents were proven at the start of the experiment. The ability of the antagonistic bacteria to inhibit growth of all three pathogen species was evaluated by using antibiosis test and agar-well diffusion test. The isolate which produce the widest inhibition halo were identified by physiological, biochemical and morphological tests. The isolates were rod shaped, gram negative and oxidase and catalase positive. The ability of the isolate to form Biofilm and to produce indole acetic acid (IAA) were evaluated. Biofilm formation by the microplate method showed high absorption at 660 nm which reflected the high ability of the isolates in production of Biofilm. A fragment of the 16s rDNA of a representative isolate was amplified by PCR using universal primer pairs (FD1,RD1) and sequenced by Macrogen co. (Macrogen, South Korea). The nucleotide sequence of the 16s rDNA gene of the isolate had more than 98% identity with those of Delftia acidovorans. this is the first report on isolation of D. acidovorans controlling possessing the potential to inhibit growth of the causal agents of fire blight and citrus blast disease under laboratory conditions.