جداسازی با کتری های اپیفیت دارای پتانسیل آنتاگونیستی علیه Xanthomonas translucens گندم

Wheat is one of the most important grains in the field of food security. Annual biotic and abiotic stresses cause great damage in the field of wheat production. The use of poisons and chemicals to improve growth conditions and control biological stress is widely used due to their rapid effects. But due to the investigation of its effects on the health of the consumer and the residual poisons in the consumed product, attention has been directed to the use of alternative methods of chemical poisons. The use of antagonistic microorganisms and PGPR agents is one of these solutions. In this research, with the aim of isolating bacteria with antagonistic potential against X.translucens, healthy wheat plants were collected from the various wheat cultivation areas in Razavi Khorasan province, and their epiphyte bacteria were isolated. The halo test was performed by spotting isolates on the NA medium and then spreading the X.translucens suspension on the culture media. The diameter of the halo formed around the colony of isolates were evaluated. Greenhouse experiments were done on 2-month-old wheat seedlings cultivar Falat, by two methods of spraying the leaves with a freshly prepared suspension of epiphyte isolates and immersing the roots in a suspension of antagonist isolates with a population of 1x108 CFU/ml. Pathogen inoculation was done 2 days after inoculation of epiphyte isolates by leaf cut method. 3 repetitions were considered for each of the isolates. Examining the length of the lesion after 15 days showed that the disease reduction index ranges was variable from 11.442 ± 3.106 % to 90.196 ± 0.849%. The best isolates after examining the antagonistic test against X.translucens, were evaluated for production of extracellular enzymes. Among the 32 isolates, the isolates Rh124 (22.66 ± 6.65mm (, Ph20(19 ± 2mm), Ph8(16.33 ± 1.52 mm), Rh38 (16.33 ± 2.08 mm) had the highest halo diameter in cellulase production assay in CMC agar medium. The isolates Ph8(40.33 ± 1.52mm), Ph20(35.33 ± 2.08mm), PhB41 (35.33 ± 1.15mm), RhE10 (34.66 ± 0.57mm) formed the highest halo diameter in protease assay in skim milk agar medium. None of the isolates produced pectinase. The Ph8 (27.66 ± 2.51mm), Ph20 (23.33 ± 1.52 mm), Rh124 (23.33 ± 3.05 mm), Rh42 (22.66 ± 3.21 mm), PhB113 (22.66 ± 1.52 mm) also indicated halos with bigger diameter in amylase analysis on starch agar medium. Wheat plant growth factors including fresh weight, dry weight, length of plant organs also are measured in greenhouse conditions. As a result, the Ph8 and Ph20 isolates, which had the highest ability to reduce disease symptoms and increase the growth quality of seedlings, were identified according to molecular sequencing and biochemical tests, these two isolates were identified as Bacillus thuringiensis and Stenotrophomonas maltophilia, respectively.