Renata Baličević

NEMATODE COMMUNITIES AS BIOINDICATORS OF ANTROPOGENIC INFLUENCE IN AGROECOSYSTEMS

Nematode communities showed possibilities to be good indicators of different kind of disturbances in ecosystems. Some groups of nematodes can survive under disturbed environmental conditions, while others cannot. The objective of this investigation was to determine if the nematode communities in the soil could serve as bioindicators of anthropogenic activities in agroecosystems. Research was conducted in 2000, in Kneževo near Osijek. The nematode communities were investigated on three different soil treatments: Poplar forest, Arable land with standard tillage regimes – wheat, Arable land with standard tillage regimes – corn. Sampling was done using a corer O 2 cm, to a depth of 20 cm. There were 4 replicate plots of each treatment. Nematodes were extracted from 100 g subsamples of soil by the Seinhorst method (Seinhorst, 1956). Identification was done by using keys of Bongers (1994), Mai & Lyon (1975) and Andrassy (1984). Total number of nematodes and number of genera were determined and compared between treatments, as well as Maturity index (MI), Plant parasitic index (PPI) and PPI/MI (Bongers, 1990). Trophic structure was determined according to Yeates et al. 1993. Abundance of nematodes was higher in agricultural treatments in compare to treatment without human intervention (poplar). In opposite, number of genera in treatments was highest in poplar, while in agricultural soil, number of genera that survive was lower. Trophic structure analyses showed similar patterns in all treatments investigated. Five trophic groups occurred (bacterivorous, fungivorous, plant-feeding nematodes, omnivorous and predators). Plant - feeding nematodes were dominant in poplar treatment while in agricultural treatments dominated bacterial feeding nematodes followed by plant feeding nematodes. Although MI and PPI do not show statistically significant differences among treatments the trends in them do represent an effective tool as distinguishing parameters of anthropogenic influence in agro ecosystem. The obtained results provide us information that nematode communities in the soil could serve as reliable bioindicator of anthropogenic activities in agro ecosystems.

Croatian diatomites and their possible application as a natural insecticide

In recent decades, there has been an increase in the use of diatomaceous earth (DE) as a natural insecticide because of its low mammalian toxicity, worker safety, low risk of food residues and the occurrence of resistant insect populations associated with the use of chemical insecticides.Therefore there is potential for research into known but previously undescribed Croatian mid-Miocene marine diatomites from the perspective of their potential as proper DE that could be mixed with plant extracts as a new formulation for grain storage protection. The marine diatomites belong to the Paratethyan near shore environment, deposited in the upwelling zone during a mid-Miocene temperate climate. Palaeontological, mineral and geochemical analyses were done on ten promising marly sediments from 26 outcrops and one borehole from the North Croatian Basin. The most important ingredient of diatomaceous sediments is silica (biogenic opal-Aand SiO2 bound in other silicate minerals including quartz, clay minerals, micas, etc.). The amorphous silica content of the tested Croatian diatomites is relatively low (<50%) in comparison with the Celatom® MN 51 standard (medium to high efficient DE) (73.6%), nevertheless they show insome part even slightly better efficacy against insects. It seems that the enhanced content of smectite in diatomaceous sediments also influences increased absorption of DE. Based on palaeontological results, the most efficient diatomites from the Podsusedsko Dolje and Markusevec (Medvednica Mt.) consist of the mid-sized planktonic Coscinodiscus group of species whereThalassionema nitzschioides dominate and is positively correlated with their absorption. The usage of Bostroms’ standard formula for getting opal-A from geochemical data was abandoned because of negative results and the modified Murdmaas’ formula for hemipelagic sediments was applied. Preliminary results on the aforementioned diatomite (as inert dusts) show good efficacy against tested insects Sitophilus oryzae (LINNAEUS), Tribolium castaneum (HERBST) and Rhyzopertha dominica (FABRICIUS).

Fusarium species isolated from plant debris in eastern 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.

Toxicity of naturally occurring compounds of Dalmatian (Croatia) Lamiaceae and Lauraceae to maize weevil ( Sitophilus zeamais motsch)

Maize weevil (Sitophilus zeamais Motsch.) is the major stored pest of Coleoptera order. It belongs to the group of economically important pests of stored grain. In Croatia, maize weevil can be more frequently found in storages of small-scale farms than in large storage facilities or silos. This is ascribed to its higher resistance to lower temperatures in distinction from the remaining pests of Sitophilus genus. Present measures of stored pest control are mainly based on application of synthetic insecticides and fumigants. However, their non-selective and uncritical application in storage facilities brings up some serious issues, such as toxic effects to the grain that is used in diet for people and livestock (Fishwick, 1988), and contamination of the environment (WMO, 1995). In practice in Croatia, phosphine is presently in use in stored pest control. However, fumigation with phosphine should be also limited for evident increase in the resistance of some pest species to a phosphine compound, which has been observed in more than 45 countries (Bell and Wilson, 1995). This means that phosphine in use can and has to be limited on the global level. Therefore, there is a necessity to find safe alternatives to the conventional insecticides and fumigants that would protect grain and its products (Rozman et al. 2006). This investigation proved that certain compounds (monoterpenes) of Dalmatian essential oil extracts of the families Lamiaceae and Lauraceae, respectively: lavender (Lavandula angustifolia Ch.), laurel (Laurus nobilis L.), rosemary (Rosmarinus officinalis L.) and thyme (Thymus vulgaris L.) exhibited toxic activity against maize weevil S. Zeamais which could be used as a new alternative in protection against the pest species.

Dormancy and germination of Johnson grass seed (Sorghum halepense (L.) Pers.)

Cilj istraživanja bio je utvrditi ucinkovitost razlicitih metoda prekida dormantnosti sjemena sirka (Sorghum halepense (L.) Pers.) odnosno njihov u

Influence of K excessive soil and plant supply on Ca deficiency in pepper fruits (Capsicum annuum L.)

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.

Influence of Substrate in Biological Control of Tomato Seedlings against Rhizoctonia Solani and Pythium Debaryanum

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.

Control of soil parasites ( Pythium debaryanum, Rizoctonia solani ) on tomato by a biological product

The purpose of phytomedicine nowadays is ecologically acceptable protection against plant diseases that is meant to be attained by reducing standard chemical plant protection applying preventive protection measures and the newest achievements in biological control. In current vegetable production soil parasites (Pythium debayianum, Rizoctonia solani) are found to be a serious issue, particularly in seedling production. The aim of our research was evaluation of biological control of parasites by biological product and its efficiency relating to be standard chemical products in greenhouse production.