Anđelko Opačak

Heavy metal concentrations in the liver of two wild duck species: influence of species and gender

Abstract The risk of wild ducks exposure to heavy metals in the environment was assessed by analyzing 20 wild ducks shot in the hunting area at the fish farm in Donji Miholjac, Eastern Croatia. Liver samples obtained from 10 Mallards and 10 Common Pochards were examined for heavy metals (Cd, Pb, As, Hg) by using flame atomic absorption spectrophotometry (AAS). Significant difference in heavy metal content between analyzed species was confirmed only for Cd (P≤0.01), and no differences were found between genders within species. The results obtained suggest the importance of wild ducks as bioindicators of heavy metal pollution, especially Common Pochard for Cd, and Mallard for Pb accumulation.

Influence of biotic and abiotic environmental conditions on sunflower (Helianthus annuus L.) grain yield

Way of pollination in sunflower is allogamy and therefore the presence of insects is essential for successful production. Trial material was consisting of six sunflower hybrids that were grown on majority of sunflower’ s fields in Croatia. Trial was conducted on trial-field situated in Kneževi Vinogradi (Baranja region). Honey bees were transported in Langstroth-Rooth (LR) beehives to the trial field ; three days before sunflower’ s blooming. Impact of honey bee on selection and production traits of sunflower was expressed as a difference between results gained by free pollination and results under the condition of isolation. The most important pollinator of sunflower is a honey bee. Weather conditions (air temperature, relative air humidity and rainfalls) considerably influenced activities of honey bees during sunflower blooming. Honey bees were mostly active during the days without rain, at air temperature from 23 to 26 oC and relative air humidity from 65 to 75 %. The most attractive hybrid for honey bee was hybrid H4. Presence of pollinators resulted in improvement of selection and production traits of sunflower: number of flowers per head, number of full up field grains per head, percentage of pollination, 1000 kernel weight, hectolitre mass, oil content and oil yield.Considerable economic rationale was determined for the introduction of pollination with honey bee in agriculture practice.

The impact of habitat on distribution of Giant liver fluke (Fascioloides magna) in eastern Croatia

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.