Duran Özkök
@kayseri.edu.tr
Assistant Professor
Kayseri Universitesi
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Ugur Azizoglu, Gholamreza Salehi Jouzani, Nihat Yilmaz, Ethem Baz, and Duran Ozkok
Elsevier BV
Entomopathogenic bacteria (EPBs), insect pathogens that produce pest-specific toxins, are environmentally-friendly alternatives to chemical insecticides. However, the most important problem with EPBs application is their limited field stability. Moreover, environmental factors such as solar radiation, leaf temperature, and vapor pressure can affect the pathogenicity of these pathogens and their toxins. Scientists have conducted intensive research to overcome such problems. Genetic engineering has great potential for the development of new engineered entomopathogens with more resistance to adverse environmental factors. Genetically modified entomopathogenic bacteria (GM-EPBs) have many advantages over wild EPBs, such as higher pathogenicity, lower spraying requirements and longer-term persistence. Genetic manipulations have been mostly applied to members of the bacterial genera Bacillus, Lysinibacillus, Pseudomonas, Serratia, Photorhabdus and Xenorhabdus. Although many researchers have found that GM-EPBs can be used safely as plant protection bioproducts, limited attention has been paid to their potential ecological impacts. The main concerns about GM-EPBs and their products are their potential unintended effects on beneficial insects (predators, parasitoids, pollinators, etc.) and rhizospheric bacteria. This review address recent update on the significant role of GM-EPBs in biological control, examining them through different perspectives in an attempt to generate critical discussion and aid in the understanding of their potential ecological impacts.
Duran Özkök and Sibel Silici
Springer Science and Business Media LLC
In this study, the total phenolic content (TPC), antioxidant activity, and free radical scavenging activities (FRSA) of 70 samples comprising honeybee products (honey, pollen, royal jelly, and propolis) and their mixtures were determined. The TPC was determined in accordance with the Folin–Ciocalteu method, antioxidant activity with phosphomolybdenum, and FRSA with the 1,1-diphenyl-2-picryl hydrazyl (DPPH) assays. Honeybee propolis showed the greatest TPC, antioxidant activity, and FRSA followed by pollen, honey, and royal jelly, respectively. A positive correlation was observed between TPC and antioxidant activity of honey, pollen and mixed samples (respectively, r=0.91, r=0.93 and r=0.92) (p<0.01). Similarly, honey and mixed samples exhibited positive correlations with TPC and FRSA (respectively, r=0.98 and r=0.92) (p<0.01). It was concluded that honeybee products and their mixtures have antioxidant activity and FRSA and these effects may be attributed to their phenolic content.
Duran Özkök and Sibel Silici
Springer Science and Business Media LLC
Hydroxymethylfurfural (HMF) is a by-product of thermal degradation of glucose and fructose. In this study, the effects of high HMF content of honey on biochemical parameters of rats were investigated. Experiments were conducted with 40 Wistar albino male rats, each weighing 250–350 g and covered a period of 5 weeks. The animals were divided into five groups. The first group was served as control group. HMF was injected subcutaneously at a dose of 200 mg/kg rat b.w. to the animals in group 2. Group 3 was fed with honey that contains 10 mg HMF/kg honey. In group 4 and 5, there were honeys that contain significantly high HMF content due to long storage period (181 mg HMF/kg honey) and heat process (140 mg HMF/kg honey). At the end of the feeding process, biochemical blood parameters of rats were investigated. It was observed that there were no differences among the glucose, triglyceride, HDL cholesterol, uric acid, Na, GGT, and ALP parameters of the groups. On the other hand, significant differences were observed among the cholesterol, LDL, BUN, creatinine, Ca, P, Mg, K, Cl, total bilirubin, LDH, CPK, AST, ALT, total protein, and pseudocholinesterase values of the rats. The highest adverse effects were obtained from group HMF, and it was followed by groups SH (stored honey) and HH (heated honey). It can be concluded that high HMF content of honey may affect the human health adversely; thus, HMF in honey must be controlled by beekeepers.
Ethem Akyol, Adnan Unalan, Halil Yeninar, Duran Ozkok, and Cahit Ozturk
Informa UK Limited
This study was carried out to determine the performances of Mugla and Nigde ecotypes (A. m. anatoliaca), Caucasian (A. m. caucasica) and Carniolan (A. m. carnica) honeybee genotypes in the region of central Anatolia conditions. A total of 40 colonies (each genotype group consisted of 10 colonies) were used in the study. All queens were reared at the same time and in the same apiary and were instrumentally inseminated. The average numbers of combs covered with bees were found to be 11.24±0.59, 9.51±0.42, 8.11±0.31 and 12.38±0.72 per colony respectively; the average brood areas were found to be 2825.0±240.3, 2160.6±176.8, 1701.9±129.7 and 2883.0±104.4 cm2 per colony respectively; and the average honey yields were found to be 28.60±0.88, 15.40±0.69, 23.40±0.54 and 31.60±1.12 kg per colony in Mugla ecotype, Nigde ecotype, Caucasian and Carniolan genotypes respectively. The mean differences among the genotypes for number of combs with bees, brood area and honey yield were significant (P<0.01). These results showed that the Carniolan genotype had the best performance and Nigde ecotype had the lowest performance in temperate climate conditions. Therefore, productivity of the Nigde ecotype can be increased by a crossbreeding programme with Carniolan and Mugla genotypes.
Duran Özkök, K. Işcan and S. Silici
Ethem Akyol, Halil Yeninar, Mustafa Karatepe, Bilge Karatepe, and Duran Özkök
Informa UK Limited
Abstract This study was conducted to determine the effects of queen age on varroa population levels in hives and performance of honey bee (A. mellifera caucasica) colonies. Levels of varroa infestation and performances of the colonies which had 0, 1- and 2-year-old queens were compared in mild climate conditions. Varroa numbers on adults and drone brood, number of frames covered with bees and brood areas were determined every month between 10 May and 10 October 2004. Overall average (± S.E.) % infestation levels of varroa were found to be 5.96 ± 1.42, 11.58 ± 1.46 and 15.87 ± 1.39% on adult bees and 21.55 ± 1.43, 31.96 ± 1.44 and 37.55 ± 1.45% in drone brood cells for 0, 1- and 2-year-old queen colonies, respectively. The colonies which had 0, 1- and 2-year-old queens produced 2673.58 ± 39.69, 2711.75 ± 39.68, and 1815.08 ± 39.70 cm2 overall average (± S.E.) sealed brood and 10.35 ± 0.24, 10.43 ± 0.26 and 7.51 ± 0.21 numbers of frame adult bees, respectively. Honey harvested from 0, 1- and 2-year-old queen colonies averaged 21.60 ± 5.25, 22.20 ± 6.55, and 14.70 ± 2.50 kg/colony, respectively. The colonies headed by young queens had a lower level of varroa infestation, a greater brood area, longer worker bee population and greater honey yield in comparison to colonies headed by old queens.