جداسازي،شناسايي و تعيين فعاليت آنزيم ACC Deaminase باكتري هاي غالب ريزوسفر كلزا در خاكهاي شور

Isolation, Identification and Determination of ACC Deaminase Activity in Canola Rhizobacteria Isolated from Saline Soils

The proper use of saline soils to produce maximum yield of crop plants has always been a big challenge in the agricultural sector. Plants, cropped in saline soils, are affected by salinity through different ways and hence, they may not reach their maximum yield. Ethylene accumulation in the roots is one of these ways, being harmful to the plants such as canola (Brassica napus). Ethylene accumulation reduces root growth and hence crop yield. If there are ACC deaminase producing bacteria in the rhizosphere, it may be likely that these bacteria change ACC precursor to a-ketobutyrate and ammonium, resulting in the decreased ethylene level in the host plant. Hence, with respect to the importance of developing canola cropping area in Iran and the necessity to plant it in saline and relatively soils, it seemed necessary that in the first step, some bacteria, with the mentioned ability, be isolated and identified. For this reason 21 combined soil samples along with the canola roots were collected from the saline and relatively saline soils of Qom and Qazvin provinces. After determining some chemical and biological properties of the soil samples, 105 strains were selected from the soil rhizosphere of canola. According to the growing abilities of the strains in the minimum media of DF having ACC, as the only source of nitrogen, it was determined that 15 strains had the ability to produce ACC deaminase. Identifying these strains, according to the microscopy, physiological and biochemical characters, mentioned in the Bergey book, entitled, Systematic Bacteriology, showed that all the strains belonged to the group of fluorescent Pseudomonads. According to the tests, related to strain determination, 14 strains were identified as P. fluorescens. Due to the lack of accordance with the characters in the Bergey book one of the strains was identified as Pseudomonas sp. Also measuring ACC deaminase activity showed that the activity of this enzyme in the isolated strains differed from 1.43 to 8.17 Mmol a-ketobutyrate/mg/hr. According to our results and in comparison with the results of other researchers, it may be beneficiary to inoculate canola seed with the identified strains to alleviate the stressful effects of salinity on canola growth and, hence yield.