Sulejman Redžepović

Influence of different Sinorhizobium meliloti inocula on abundance of genes involved in nitrogen transformations in the rhizosphere of alfalfa (Medicago sativa L.)

Inoculation of leguminous seeds with selected rhizobial strains is practised in agriculture to ameliorate the plant yield by enhanced root nodulation and nitrogen uptake of the plant. However, effective symbiosis between legumes and rhizobia does not only depend on the capacity of nitrogen fixation but also on the entire nitrogen turnover in the rhizosphere. We investigated the influence of seed inoculation with two indigenous Sinorhizobium meliloti strains exhibiting different efficiency concerning plant growth promotion on nitrogen turnover processes in the rhizosphere during the growth of alfalfa. Quantification of six target genes (bacterial amoA, nirK, nirS, nosZ, nifH and archaeal amoA) within the nitrogen cycle was performed in rhizosphere samples before nodule formation, at bud development and at the late flowering stage. The results clearly demonstrated that effectiveness of rhizobial inocula is related to abundance of nifH genes in the late flowering phase of alfalfa. Moreover, other genes involved in nitrogen turnover had been affected by the inocula, e.g. higher numbers of amoA copies were observed during flowering when the more effective strain had been inoculated. However, the respective gene abundances differed overall to a greater extent between the three plant development stages than between the inoculation variants.

Genetic diversity of Bradyrhizobium japonicum field population revealed by RAPD fingerprinting

RAPD fingerprinting was used for strain identification and the assessment of genetic diversity within a field population of Bradyrhizobium japonicum. Total genomic DNAs from 13 field isolates and two inoculant strains were amplified using six different 10‐mer primers. Different and informative band patterns were obtained for all strains analysed. Cluster analysis unexpectedly revealed that none of the field isolates was identical to inoculant strains which were regularly used for soybean inoculation. Among field isolates two highly divergent groups were determined. The results indicate that RAPD is a very discriminative and efficient method for differentiating and studying genetic diversity of B. japonicum strains.

Bacterial communities associated with the production of artisanal Istrian cheese

In this work we report on the main bacterial microflora typical for fermentation and ripening of traditional Istrian cheese. Samples from milk as well as Istrian cheese were analyzed during the ripening process by using culture independent molecular fingerprinting methods as well as culture based approaches. Our results indicate changes in bacterial diversity pattern during the ripening process. Differences in bacterial diversity at the same ripening stage among different farms investigated were comparably low. Sequence analysis of the most prominent bands of denaturing gradient gel electrophoresis fingerprints revealed dominance of Lactococcus lactis subs. lactis in all samples and a strong presence of Enterococcus spp. which was also confirmed by plate count analysis.

Influence of plant growth regulator and rhizobial inoculation on nodulation and soybean nitrogen contant

Sustainable agriculture production greatly relies on the use of renewable resources of nitrogenous reserves and rational nitrogen fertilization. The inoculation of cultivated leguminous plants with selected rhizobial strains is recommended to maximize the contribution of biological nitrogen fixation to the nitrogen status of the host plant. Considering that symbiotic fixation is dependent on the photosynthetic capacity of the specific legume, special efforts have been taken to find patterns of increasing plant photosynthetic capacity. The main aim of the present study was to evaluate the influence of Bioalgeen-S90 as a growth regulator and soybean inoculation with different B. japonicum strains on nodulation and soybean nitrogen and protein content in agroecological conditions of eastern Croatia. At location Karanac application of Bioalgeen-S90 significantly increased nodule number, nodule dry weight and seed protein content compared to plots without Bioalgeen-S90 application. Statistical analysis showed superior effect of inoculation, irrespective of the strain used, compared to to control uninoculated plots for all measured properties. Significant influence of inoculation with B. japonicum strain USDA 110 on nitrogen content in stem and ureide content in xylem were determined compared to plots inoculated with strain D344. At location Mirkovac application of Bioalgeen-S90 significantly increased nodule number, ureide content in xylem and seed protein content compared to plots without Bioalgeen-S90 application. Inoculation with strain D344 significantly increased nodule number and nodule dry weight, ureide content in xylem and nitrogen content in soybean aerial parts compared to variants inoculated with strain USDA 110 and control variants.The results of this study clearly showed the positive effect of growth regulator Bioalgeen-S90 and rhizobial inoculation on nitrogen status of host plant. However, further investigations under different agroecological conditions are needed.

Symbiotic nitrogen fixation and sustainable soybean production

One of the biggest challenges for the safe maize production is the yield stability in a wide range of environments with different soil fertility, weather conditions, prevailing pests and diseases as well as cultural practices. In order to achieve it, new hybrids with higher tolerance to biotic and abiotic stress are continuously being created. In order to compare performance of maize hybrids in environments with different levels and types of stress, and relate it to the stalk lodging incidence, we compared performance of 64 maize hybrids obtained by crossing 16 inbred lines with four inbred testers in three different environments. Two environments at same location (Rugvica) differed in crop rotation, and the third environment at location Botinec was considered as dry because of low water capacity of the soil. Mixed models that included all design elements and genetic background of hybrids were used to analyze the effect of lodging on yield in different environments. The results show that stalk lodging had a significant effect on yield, but significant lodging x environment interaction indicates that this effect was rather environment specific.Sweet pepper Istra F1 hybrid was grown in a greenhouse on K rich soil. For evaluation of K antagonism, two K rates (55 and 85 kg ha-1) were applied in a randomized complete block design with four replications. Total number of fruits, total number of BER affected fruits as well as average fruit mass were recorded for each harvest. Fruit and leaf K and Ca content were determined at three plant growth stages (at the stage of the first, third and fifth fruit cluster). Higher K rate gave higher : average fruit mass (169.45 g), total number of fruits per plant (7.95), number of BER affected fruits per plant (3.82), K in leaves (5.44% DM), K in fruits (6.35% DM), but negatively correlated with Ca concentration in fruits (0.57% DM) and leaves (3.24% DM). This resulted in decreased marketable yield of sweet pepper fruits.