Effect Of Molybdenum On Rhyzobium Growth And Stylosanthes-Rhizobium Symbiosis

Stylosanthes spp. is an important leguminous forages, often match with gramineous pasture for grazing or green fodder. The yield and quality are the key indicators in the measurement of Stylosanthes guianensis. After the inoculation of rhizobium bacteria, the yield and nitrogen content of Stylosanthes guianensis can be improved. In the process of rhizobium biological nitrogen fixation, molybdenum is the essential element. Too much or too little content of molybdenum are bad for the nitrogen-fixing process. By researching the qualitative and quantitative determination in four rhizobium strains under different molybdenum concentration growth situation in solid and liquid medium, determine the molybdenum range and optimal growth molybdenum concentration of different strains, had been got by the qualitative and quantitative determination of the growth of the four rhizobium strains under different molybdenum concentration in solid and liquid medium. Experiment of sand culture was used to test the influence of different molybdenum concentration in soil environment to the symbiotic system by soil culture. Determined the molybdenum concentration which has the best nitrogen fixation effect, and test the root nodules rate under all processing conditions through the molecular means. The main research results are as follows:(1) Strains of LZ3-2and PN13-3have the widest range of molybdenum concentration tolerance0-0.45%, StrainsYM11-1take second place0-0.40%, Strains RJS9-2is the poorest0-0.35%. When molybdenum concentration up to0.45%, strains grow very slowly, and even stop growing; The optimal molybdenum concentration for growth of strains LZ3-2, YM11-1, RJS9-2and PN13-3are0.25%,0.10%,0.05%and0.15%; When the molybdenum concentration range beyond a certain value, the growth of rhizobium is restrained, even slower than strains which without the processing of molybdenum.(2) The plant height, fresh weight, nitrogen content, nitrogenase activity and the number of root nodules of Stylosanthes guianensis all show that:With the inoculation of rhizobium bacteria, strains YM11-1and RJS9-2have better nitrogen-fixing ability when the molybdenum concentration in or under0.10%, Strains PN13-3’s suitable molybdenum concentration is between0.10%and0.25%, Strains LZ3-2still have strong nitrogen-fixing ability when the molybdenum concentration is greater than0.15%.(3) The results of sand culture and soil culture show that:Rhizobium bacteria can effectively reduce the absorption of molybdenum in plant. Strains RJS9-2did the worst while strains LZ3-2did the best in the two varieties.(4) Strains of LZ3-2and Strains PN13-3have the highest rates of root nodules in the collocation of four strains with two varieties for68.67%and80.00%. When the molybdenum concentration is0.25%, strains RJS9-2have the lowest rate of root nodules27.33%and12.33%respectively.(5) In gusA gene markers, there is no significant difference between marker strains and original strains while comparing the four indexes (the number of root nodules, nitrogen content, fresh weight and nitrogenase activity) between the two varieties after the inoculation of marker strains and original strains by water culture.