engleski

Influence of different Sinorhizobium meliloti inocula on nitrogen transformations in bulk soil, rhizosphere and nodules of alfalfa

In sustainable agriculture besides the application of organic fertilizers, biological N2 fixation (a microbiological process that converts atmospheric nitrogen into plant-usable ammonium ) plays a crutial role in the input of nitrogen into the soil. In this respect legumes are of central improtance: Besides their economic value as crops, they contribute substantially to the overall N economy of the system as intermediate crops. Their symbiosis with nitrogen fixing Rhizobia are the driving force for the positive nitrogen balance. However this effect does not depend only on the capacity to fix elementar nitrogen from the air, but also on the internal nitrogen turnover in the symbionts as well as in the soil and rhizosphere microflora. Therefore we performed a pot experiment in the greenhouse to determine the inoculation effect of alfalfa seeds with two different indigenous S. meliloti strains on the abundance of genes and transcripts involved in N turnover processes in the bulk soil, the rhizosphere, and the nodules. Quantification of the target genes nirK and nirS (nitrite reductases, denitrification), amoA (ammonia monooxygenase, nitrification), nifH (nitrogenase, N2 fixation) and npr (neutral metalloprotease, N mineralization) was performed by real-time PCR using SybrGreen. Samples have been taken before and after nodule formation as well as in the early flower stage. In the meeting data about abundance of the mentioned genes in the different treatments will be presented.

N cycle; rhizosphere; Sinhorizobium meliloti; alfalfa

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