Mihaela Blažinkov

Biogeography of Sinorhizobium meliloti nodulating alfalfa in different Croatian regions

Sinorhizobium meliloti is a nitrogen-fixing rhizobium symbiont of legumes, widespread in many temperate environments the high genetic diversity of which enables it to thrive as a symbiont of host legumes and free-living in soil. Soil type, together with geographic differences and host plant genotype, seem to be prominent factors in shaping rhizobial genetic diversity. While a large body of research supports the idea that the genetic structure of free-living microbial taxa exhibits a clear biogeographic pattern, few investigations have been performed on the biogeographic pattern of S. meliloti genotypes in a restricted geographic range. In the present study, a collection of 128 S. meliloti isolates from three different regions in Croatia was investigated to analyze the relationship between genetic diversity, geographic distribution, soil features and isolate phenotypes by using amplified fragment length polymorphism (AFLP) as a genome-wide scanning method. Results obtained led to the conclusion that the genotypes of isolates cluster according to the region of origin and that the differentiation of S. meliloti populations can be mainly ascribed to geographic isolation following an isolation-by-distance model, with a strong distance-decay relationship of genetic similarity with distance, in which local soil conditions are not the major component influencing the isolate phenotypes or their genomic differentiation.

Yield and height of alfalfa (Medicago sativa L.) effected by rhizobial inoculation

Forage crops constitute the major component of dairy feeds and legumes have been viewed as excellent sources of N in agriculture.Biological nitrogen fixation by leguminous plants is a significant source of available N in both natural and managed ecosystems and that unique ability makes legumes especially valuble in forage program.Alfalfa is one of the most important protein sources for nutrition of livestock.As a legume, alfalfa forms symbiotic relation with nitrogen fixing bacteria Sinorhizobium meliloti, which symbiotic efficiency is determined by their individual genotype.The aim of this study was to determine the infuence of cultivar type of alfalfa and S.meliloti strain on forage yield and height of plants.Results of 2 years experiment revealed that DM yield was significantly higher with cultivars OS 88 and Mirna compared to other two cultivars (Posavina and OS 66). The effect of cultivars by strains was not significant, so inoculated cultivars performed significantly better DM yields in comparison to control (no inoculation).

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.

The effect of rhizobial inoculation and liming on alfalfa production in Croatia

Maize (Zea mays L.) genotypes wit It improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha(-1)) and low-N (1100 kg N ha(-1)) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1 in the low-yielding (dry) environment to 55 kg grain kg N-1 under higher yielding environment, When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.Hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) were evaluated as cover crops during two vegetation seasons in the Mediterranean and Continental area of Croatia. Better tolerance to low winter temperatures was observed for crimson clover. Higher plants (10 to 3 1 cm) before winter and in spring (67 to 117 cm) were measured for hairy vetch, while crimson clover had higher yields of fresh biomass (33.7 to 113.1 t ha(-1)). Concentrations of N (1.53 to 3.34%), P2O5 (0.55 to 1.04%) and K2O (2.02 to 5.32%) in plant tissue were higher for hairy vetch. However, due to higher yields of dry matter, crimson clover accumulated more N (105 to 239 kg ha(-1)), P2O5 (28 to 83 kg ha(-1)), and K2O (105 to 440 kg ha(-1)) than hairy vetch. According to our results crimson clover could be recommended as a cover crop in Mediterranean and Continental area of Croatia.

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.