Zur Wirkung von Milchsäure auf den Varroa-Befall der Biene

40% lactic acid was sprayed 3 times into each of two bee colonies. The rate of infestation was determined, before beginning the experiment and after each of the applications. The treatments showed a mean percentage reduction in the brood infestation byVarroa of 76,7% in the first colony and 85,2% in the second. These data indicate that it is possible to control the Varroasis by means of lactic acid successfully and without side effects.     

Attractiveness of the parasitoid,meteorus rubens (nees) to hexane-extract ofagrotis ipsilon (hufn.)

The braconid parasitoidMeteorus rubens (Nees) is a gregarious larval parasitoid ofAgrotis ipsilon (Hufn.). An olfactometer was used to check the attractiveness of the parasitoid to Hexane extract (kairomone) of its host that could be used in conjunction with releases of natural enemies. Female wasps are attracted in high numbers to the kairomone, compared with males. Respective rates of 94.3 and 22.3% are reported. In the control (no kairomone was used), the corresponding figures are 5.7 and 3.3%.     

Metabolic characterization of Brassica rapa leaves by NMR spectroscopy

The Brassica has been intensively studied due to the nutritional and beneficial effects. However, many species, varieties, and cultivars of this genus and the resulting large metabolic variation have been obstacles for systematic research of the plant. In order to overcome the problems posed by the biological variation, the metabolomic analysis of various cultivars of Brassica rapa was performed by NMR spectroscopy combined with multivariate data analysis. Discriminating metabolites in different cultivars and development stages were elucidated by diverse 2D-NMR techniques after sorting out different significant signals using (1)H NMR measurements and principal component analysis. Among the elucidated metabolites, several organic and amino acids, carbohydrates, adenine, indole acetic acid (IAA), phenylpropanoids, flavonoids, and glucosinolates were found to be the metabolites contributing to the differentiation between cultivars and age of Brassica rapa. On the basis of these results, the distribution of plant metabolites among different cultivars and development stages of B. rapa is discussed.     

Prevalence of bluetongue virus antibodies and associated risk factors among cattle in East Darfur State,Western Sudan

Background

Bluetongue virus (BTV) is an insect-transmitted virus, which causes bluetongue disease (BT) in sheep and a fatal hemorrhagic infection in North American white-tailed deer. However, in cattle the disease is typically asymptomatic and no overt clinical signs of disease appear to be associated with BTV infection. Serological evidence and isolation of different BTV serotypes have been reported in Sudan, however, no information is currently available in regard to previous exposure of Sudanese livestock to BTV infection in East Darfur State, Sudan.

Aims

To determine the prevalence of BTV antibodies and to identify the potential risk factors associated with BTV infection among cattle in East Darfur State, Sudan.

Methods

A total of 224 blood samples were collected randomly from five localities in East Darfur State, Sudan. The serum samples were screened for detection of BTV-specific immunoglobulin G (IgG) antibodies using a competitive enzyme-linked immunosorbent assay (c-ELISA).

Results

Serological evidence of BTV infection was observed in 150 out of 224 animals accounting for a 67% prevalence rate among cattle in East Darfur State. Older cattle (>2 years of age) were six times more likely to be infected with BTV (OR = 6.62, CI = 2.87-15.26, p-value = 0.01). Regarding animal source (contact with other herds) as a risk factor, it was shown that cattle purchased from market or introduced from other herds were 3 times at higher risk of being infected with BTV (OR = 3.87, CI = 1.07-13.87, p value = 0.03). Exposure of cattle to the insect vector increased the risk of contracting BTV infection by six times compared to non-exposed cattle (OR = 6.44, CI = 1.53-27.08, p value = 0.01).

Conclusion

The present study indicated that age, animal source and the intensity of the insect vector are influential risk factors for BTV infection in cattle in the Darfur region. Surveillance for BTV infection should be extended to include other susceptible ruminants and to study the distribution of the insect vectors to better predict and respond to a possible BTV outbreak in the State of East Darfur, Sudan.     

Effects of physical attributes and chemical composition of novel foods on food selection by Norway rats (Rattus norvegicus)

An organism’s food is a fundamental aspect of its survival niche. Free-ranging rodents are presented regularly with different types of novel food. To investigate the novel food selection process in Norway rats concerning chemical and physical characteristics, 288 laboratory bred Norway rats (Rattus norvegicus) were tested with a 2-h free choice for each animal. First, rats were tested against eight kinds of novel foods: corn, beans, broiler ration, soybeans, peanuts, rice, potatoes, and millet. Rats preferred corn over the other novel food types, and there was a significant positive correlation between the selective coefficient and carbohydrate content; rats chose novel food with highest energy content. Rats also appeared to be less neophobic to foods of high sugar content. Regarding physical characteristic, rats effectively differentiated between spectral colors of different wavelengths, and red-colored food was more attractive for rats than foods of four other colors. Small-sized food received the highest numbers of visits and longest feeding bouts compared to other sizes. These results suggest that the carbohydrates content, red color, and small size of novel food play a role in the novel food selection of Norway rats.     

Determination of Heat Requirements and Effective Heat Summations of Some Pomegranate Cultivars Grown in Southern Anatolia

Temperature (high and low) is one of the most limiting environmental factors for growth and production of fruits in different parts of the world. For temperate-zone fruit species, a certain total heat requirements are needed in order to obtain ripe fruits. The aim of this study was to determine heat requirements of three commercial pomegranate cultivars (‘Suruc’, ‘Katirbasi’ and ‘Hicaznar’) grown in Southern Anatolia region. The cultivars showed a narrower range of heat requirements for flowering (growing degree hours, GDH), i.e. ‘Suruc’ (25,000), ‘Katirbasi’ (25,270), ‘Hicaznar’ (28,000) and a wide range of heat requirements for fruit ripening, i.e. ‘Suruc’ (73,670), ‘Katirbasi’ (74,105) and ‘Hicaznar’ (88,052) GDH. Under the Sanliurfa province conditions, two years average of effective heat summation requirement from bud swelling to 50 % flowering stage for ‘Suruc’, ‘Katirbasi’ and ‘Hicaznar’ cultivars are calculated as 643, 655 and 718 growing degree days (GDD) and from bud swelling to harvest are 2734, 2802 and 3289 GDD. It can be concluded that the effective heat summation of Sanliurfa province is enough for commercial growing for all pomegranate cultivars.     

Quantifying the dietary biotin requirement of the catfish,Clarias batrachus

Asian catfish, Clarias batrachus, were fed semi-purified basaldiets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg^–1diet for 60 days. Fish fed the control diet (no biotin) showed(P < 0.05) higher mortality, lower weight gain, specificgrowth rate (SGR), feed efficiency ratio (FER) and protein efficiencyratio (PER) than in fish fed diets supplemented with biotin. The highestweight gain, SGR, FER and PER were noticed in fish fed 1 mg biotinkg^–1, followed by 0.5, 5, 3 and 0.1 mg biotinkg^–1, except for PER (followed by 0.5, 5, 0.1 and 3 mgbiotin kg^–1). Quadratic analysis showed that the optimumdietary biotin requirements for maximal weight gain, PER and PER were2.49, 2.54 and 2.52 mg kg^–1, respectively. Liver biotinconcentrations were influenced by levels of biotin in the diet.Concentration of liver biotin increased as level of dietarysupplementation increased and no biotin was detected in the liver of thecontrol fish. Liver pyruvate carboxylase and acetyl CoA carboxylaseactivities were higher in fish fed biotin-supplemented diets than incontrols. Biotin concentrations, pyruvate carboxylase and acetyl CoAcarboxylase activities in liver associated with normal growth rangedfrom 10.59 to 10.66 g g^–1, 147.97 to 148.18 units mgprotein^–1 and 12.76 to 12.78 units mg protein^–1, respectively. Biotin deficiency symptoms such as anorexia, darkskin colour and convulsions were observed in fish fed the control diet.The optimum dietary biotin requirement for maximal growth of C.batrachus is about 2.49 mg kg^–1 diet.     

Morphological development of post hatch larval goldlined seabream Rhabdosargus sarba (Forskål, 1775)

Ultrastructural changes in Rhabdosargus sarba larva in early life history were investigated. At hatching, the digestive system was histologically undifferentiated. The digestive tract was a straight tube attached to the dorsal end of the yolk‐sac and was not connected to either the mouth or the anus. The layer of gut epithelium at some regions of the luminal surface was straight and microvilli were not present. These straight borders were not observed at 1 day post hatching (DPH) onwards as microvilli increased in number on the luminal surface and became more regular. At 2 DPH, the digestive system was well differentiated and the separation of the mid‐ and hindgut by the intestino‐rectal valve became more advanced. At 0 DPH, the eye was spherical and the retina had a zonation with undifferentiated cells. The eye also lacked differentiated photoreceptors (PR). The retinal PRs increased in length and in number as the yolk‐sac was absorbed. By 2 DPH, the eye was fully pigmented, suggesting that the larval vision system was functional. The larvae had a pure cone retina at the onset of exogenous feeding. Morphological and functional differentiation of the digestive tract and the eye of the larvae preceded the completion of yolk and oil globule absorption. The oil globule was exhausted at 4 DPH and at 2 DPH, the yolk‐sac was completely absorbed. Food particles were observed at 3 DPH. Food particle ingestion and absorption of the yolk‐sac were observed as vision became fully functional.     

Water Relations, Abscisic Acid and Yield of Wheat Plants in Relation to the Interactive Effect of Seawater and Growth Bioregulators

Irrigation of wheat plants with seawater (10 and 25 %) led to significant increases in free and bound abscisic acid (ABA) in leaves, especially at 25 %. The relative water content (RWC) and water use efficiency (calculated from grain yield, WUE_G, or from biomass yield, WUE_B) of the seawater-irrigated plants were lower than those of the control. Grain pre-soaking in gibberellic acid (GA₃), indole-3-acetic acid (IAA) or ABA reduced the levels of accumulated ABA (free and bound) produced by seawater irrigation. The stress imposed by seawater generally reduced yield and yield components of wheat plants and the effect was more pronounced at the higher level of seawater irrigation (25 %). Furthermore, seawater treatments decreased the carbohydrate content and increased the protein content of the developing grains. The effect of seawater treatments on ion concentrations in the developing grains was not consistent. The application of growth bioregulators appeared to mitigate the effect of seawater salinity stress on wheat productivity. GA₃ was the most effective hormone in this regard. The economic yield (grain yield) had a strong positive correlation with RWC, WUE_G, WUE_B, plant height, shoot fresh and dry weight, grain number/main spike, kernel weight and harvest index.     

Response of Rapeseed (Brassica napus L.) Growth, Yield, Oil Content and Its Fatty Acids to Nitrogen Rates and Application Times

A steady and progressive increase in rapeseed yield was observed with each increment in applied nitrogen rates up to 213 kg/ha in both seasons. As for nitrogen application times, the analyzed data showed that adding a split dose (either 1/2 or 1/3) before the third irrigation was a common part between high yielding treatments in 1985/86 season. Nitrogen rates X application times interaction affected rapeseed yield significantly during the first winter season. The highest seed yield of 2.5 t/ha was obtained by adding 213 kg N/ha in two split doses at sowing and just before the third irrigation. The second yield value of 2.47 t/ha was produced under the same N rate when applied in two split doses before second and third irrigation. However, in the second season (1986/87), rapeseed plants did not exhibit significant responses to nitrogen rates X application times interaction.
Chemical analyses showed that rapeseed oil content and its fatty acids (Palmetic, Stearic, Oleic, Linoleic, Linolenic, Arachidic and Erucic) percentages were not significantly affected by either nitrogen rates or application times in both seasons. A very low content of Erucic acid (0.1–0.9 %) in all tested sample was noticed.