Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)最新文献

{"title":"Changes in the microbiology of activated sludge upon the addition of iron salts with or without nitrite or nitrate.","authors":"Sarah Philips,&nbsp;Willy Verstraete","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Iron salts are frequently used in activated sludge treatment as coagulants or to improve reactor performance. However, the effect of the iron salts on the microbiology has received little attention. Furthermore, the interaction of iron ions with nitrite or nitrate present in the sludge has not been considered. In this research, the influence of ferrous and ferric iron additions, and their possible interactions with nitrite or nitrate at levels of a few mM, on the activated sludge microbiology of semi-continuous bench-scale reactors were examined. Conventional as well as molecular techniques have been used to investigate the microbial communities. Microscopic investigations showed that repeated addition of ferric iron at 2 mM gave rise to breaking of the sludge flocs, resulting in massive growth of sessile-protozoa and lowering of the numbers of nitrifiers. Ferrous iron at the same dosage resulted in large coherent flocs. Nitrite hereby seemed to enhance the detrimental effect of the ferric iron on the floc structure, whereas nitrate had a neutralizing character. 16S rRNA gene analysis showed a clear impact of the different iron respectively nitrogen treatments on the composition of bacterial communities. Cloning the sludge samples revealed the increased presence of denitrifying Feoxidizing bacteria in both the Fe(II) and Fe(III) reactors, suggesting a redox-state cycling between Fe(II) and Fe(III) in the mixed liquor.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 1","pages":"35-50"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22164480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The use of legume trap crops for control of Striga hermonthica (Del.) Benth. in sorghum (Sorghum bicolor L. Moench) in northern Nigeria.","authors":"Nuhu A Gworgwor","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Two different field trials (one trial on sorghum intercropped with groundnut [Arachis hypogaea L.], and another trial on sorghum intercropped with bambara groundnut [Vigna subterranea L. Verdc.]) were conducted during the 1995 and 1996 rainy seasons at the Teaching and Research Farm of the Department of Crop Science, Faculty of Agriculture, University of Maiduguri, Maiduguri (11 degrees 51' N; 13 degrees 15' E) to evaluate the effect of intercropping resistant and susceptible sorghum varieties with the two legume crops for the control of Striga hermonthica (Del.) Benth, in sorghum. The sorghum varieties used for both trials were ICSV 1002, ICSV 1007 (resistant varieties) and War-warabashi (susceptible). Ex-Dakar variety of groundnut was used for the sorghum-groundnut trial, while a creamed brown eyed local bambara groundnut was used for the sorghum-bambara groundnut trial. There were six treatments with the groundnut trial and nine treatments with the bambara trial and all were laid out in a randomised complete block design (RCBD) replicated four times. In the sorghum-groundnut trial, the results show that the intercropping of sorghum with groundnut significantly reduced Striga infestation up to 50% in sorghum in both years. Both resistant varieties supported significantly fewer number of Striga on sorghum when intercropped with groundnut compared with the sole sown susceptible variety. In both years and the combined analyses of 1995 and 1996 data, however, there was no significant difference in grain yield of sorghum due to the treatments. In the sorghum-bambara groundnut trial, the results show that Striga shoot count at harvest in sole sown ICSV 1007 was significantly lower than the ICSV 1002 variety, while the susceptible variety supported significantly higher Striga shoot count than the resistant varieties in both years and the combined analyses. Alternating stands of sorghum and bambara groundnut within the same row, in general, reduced Striga shoot count in all the varieties with a range of 56%-91% reduction than intercropping with sorghum varieties in alternate rows with bambara groundnut with a range of 45%-96% reduction, or sole sorghum of each variety. This resulted in significantly higher grain yield of ICSV 1002 (1175.0 kg ha-1 in 1995, 814.8 kg ha-1 in 1996, and 994.9 kg ha-1 in the combined data) than ICSV 1007 (892.6 kg ha-1 in 1995, 666.7 kg ha-1 in 1996, and 779.6 kg ha-1 in the combined data) when both were planted in alternate stands in the same row with bambara groundnut. This studies have confirmed the potentials of groundnut and bambara groundnut as trap crops in the management of S. hermonthica in sorghum under a dried environment.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 3","pages":"421-30"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22342126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-based mechanistic modelling of the fast dynamic plant response to sudden changes in microclimate.","authors":"Cindy Boonen,&nbsp;Daniel Berckmans","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 4","pages":"19-22"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22181206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insecticidal activity of a nonsteroidal moulting hormone agonist on mosquito larvae and effects on ecdysteroid amounts.","authors":"H Boudjelida,&nbsp;A Bouaziz,&nbsp;G Smagghe,&nbsp;N Soltani","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>The secondary effects of conventional insecticides on the environment, vertebrates and beneficial organisms have caused a move to the use of more target-specific chemicals such as insect growth regulators. Halofenozide (RH-0345) is a novel nonsteroidal ecdysteroid agonist that induces a precocious and incomplete moult in several insect orders. In the present study, the insecticidal activity of a commercial formulation of halofenozide (23% EC) was evaluated at different concentrations ranging between 8 and 32 micrograms/l. Treatment was made on newly moulted fourth-instar larvae of the mosquito, Culex pipiens (Diptera: Culicidae), and mortality was scored until adult emergence. Results showed that death in the larval stage was relatively important. Moreover, treatment caused a significant reduction in the length of the larval and pupal stage. In a second series of experiments, halofenozide was tested at two doses (LC50 = 12.58 micrograms/l and LC90 = 28.58 micrograms/l) and the ecdysteroid amounts during the fourth instar were evaluated in an enzyme immunoassay. We noted that halofenozide did not shifted the moment of the single larval ecdysteroid peak, but it caused an increase of the titre values. Finally, the compound at the highest concentration was found to increase significantly the cuticle thickness recorded at day 4 following treatment.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 3","pages":"657-63"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22341331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of extraction techniques and augers of different size.","authors":"T G van Galen-van Beers,&nbsp;E Brommer,&nbsp;L P G Molendijk","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Because of differences in winter survival of Pratylenchus penetrans after different host plants, concern arose about traditional extraction and soil sampling techniques. Possible bottlenecks are a too short incubation period of the root material for the time of year, or an auger size to small to pick up tough, fresh, root material. Two experiments were carried out to compare different auger sizes and variations on the standard Oostenbrink elutriation technique with additional filter-incubation of the organic material left on the top sieve (180 microns) of the elutriator. The hypothesis that soil sampling in a green crop results in more root material with a 2.5-cm auger, compared to a 1.3 cm auger, proved to be right. Since there was no effect on the number of P. penetrans recovered, the 1.3 cm auger is preferred because with this auger more cores are taken to gather the same amount of soil, resulting in a better estimation of the population. It appeared that highest yields are accomplished with the standard extraction-plus incubation-method described above. Every methodical effort to improve the extraction effectivity, caused only loss of nematodes. An incubation period of two weeks came out to be minimum. After this period, another 15 to 20% of nematodes could be harvested.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 3","pages":"691-8"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22341335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An integrated control of Pythium root rot of greenhouse tomato.","authors":"J C Tu","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Pythium root rot caused by Pythium aphanidermatum is one of the most important diseases of greenhouse tomatoes. Hydroponic culture exacerbates the problem. Both nutrient film technique (NFT) and recirculating growing systems pose a challenge in the control of this disease, because the pathogen, especially the zoospores, can spread easily in the recirculating solution to the whole growing system. Fortunately, hydroponically grown plants are easier to manipulate than soil grown plants, proper manipulation of root environments can lead to excellent disease control. This paper reports the development of an effective integrated control measure for pythium root rot of tomato by integrating pH, bioagent, and ultra-violet irradiation in a specific manner. This integrated control consists of three operations: a) before transplanting, the UV system is connected to sterilize the recirculating solution using 100 mJcm-2; b) after transplanting, the nutrient solution is delivered at pH 5.0 regime for five weeks followed by adjusting pH to 5.8 to 6.2 regime for one week; and c) bacterial bioagent, such as Pseudomonas is introduced into the root zone at 100 mL per plant at 10(8) bacteria mL-1 or added to the nutrient solution to arrive at 10(6) bacteria mL-1 in the solution. This report also discusses the advantages and limitations of this measure in the control of pythium root rot.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 2","pages":"209-16"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22345694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Suppression of Pythium spp. by Trichoderma spp. during germination of tomato seeds in soilless growing media.","authors":"R Aerts,&nbsp;B De Schutter,&nbsp;L Rombouts","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>In the Flemish horticulture Pythium spp. is an important pathogen of tomato plants (Lycopersicon esculenthum) in soilless growing media. Therefore some experiments were conducted to evaluate the possibility of decreasing the damage caused by Pythium spp. by Trichoderma spp. In a tray with several growing media, a suspension of Trichoderma conidia (10(6)/ml growing medium) was applied two weeks before sowing. On some objects, a compost extract (Biostimulus) was added. The growing media used in the experiment were rockwool, recycled rockwool and recycled coconut fibre. After sowing, the trays were covered with perlite. Three isolates of Trichoderma spp.: T. asperellum (Biofungus), T. harzianum (Tri 003) and Trichoderma sp. (KHK) and two isolates of Pythium spp.: P. ultimum (MUCL) en P. aphanidermatum (HRI, UK) were used. Propamocarb was used as a chemical standard. The use of coconut fibre growing medium resulted in a higher percentage (36%) of germination than the rockwool media when only Pythium spp. was used. The presence of the spontaneous developing microflora in the coconut fibre medium gave probably also a suppression of Pythium spp. For that reason the results of the suppression by Trichoderma spp. are not easy to explain and very variable on the different objects. Pythium ultimum was more suppressed than P. aphanidermatum on all the growing media and the application of all the Trichoderma isolates increased the germination percentage of tomato seeds. T. asperellum (Biofungus) gave on rockwool also a good result for the suppression of P. aphanidermatum (increasing of germination with 48%). This effect was comparable with the propamocarb treatment (48%). T. harzianum (Tri 003) gave a small suppression (22%) and Trichoderma sp. (KHK) gave almost no suppression of P. aphanidermatum (7%). When less Trichoderma conidia were applied the germination percentage decreased. The adding of a compost extract (Biostimulus) had no influence on the results. This experiment shows that application of Trichoderma conidia in the presence of Pythium spp. increases the germination percentage of tomato seeds, sowed in the used soilless growing media.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 2","pages":"343-51"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22346235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bacteriocin Serratine-P as a biological tool in the control of fire blight Erwinia amylovora.","authors":"H Schoofs,&nbsp;K Vandebroek,&nbsp;A Pierrard,&nbsp;P Thonart,&nbsp;P Lepoivre,&nbsp;T Beaudry,&nbsp;T Deckers","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Fire blight, caused by the bacterium Erwinia amylovora (Burill Winslow et al.), is the most important bacterial disease in European pear growing. It can cause a lot of damage in some countries on apple and on pear trees in orchards and also in the fruit tree nurseries. In Belgium, the disease is present since 1972. Control of fire blight in Belgian fruit orchards is made on a broad basis of measurements in and around the fruit trees. The use of an antibiotic is allowed for application only during the primary blossom period under strict controlled regulations. The use of antobiotics in agriculture is strongly discussed on the European level today and will probably disappear in the near future. Therefore, the research on fire blight control concentrates on the possibilities of biological control with antagonistic bacteria such as Pantoea agglomerans (Erwinia herbicola), Bacillus subtilis or Pseudomonas syringae strain A 506. The use of Serratine-P, a phage tail-like bacteriocin, produced by Serratia plymiticum, shows an interesting antibacterial activity against Erwinia amylovora. Its mode of action consists in the perforation of the cytoplasmic membrane of the target cell, inducing perturbations in cellular exchanges and a final lysis of the bacterial cell. In this paper some trials are discussed on the use of Serratine-P at different doses and on different infection types on pear trees. The results indicate interesting protection possibilities on blossom- and fruit infections.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 2","pages":"361-8"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22346237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oviposition plasticity in Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae).","authors":"M Danho","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>The oviposition plasticity (term used here to refer to the phenomenon whereby some insects reduce egg laying in poor conditions and increase it when conditions improve) of Sitophilus zeamais, one of the most serious insect pests to maize during grain storage, was investigated in different food resources. Whether such oviposition plasticity exists, it can be investigated by finding if more eggs are subsequently laid by insects previously kept on unfavourable environment than by insects previously kept on favourable environment. Virgin male/female pairs of maize weevils were raised on different feeding treatments consisting of maize grain (favourable environment) or maize flour (unfavourable environment). After 1 or 3 weeks exposure, all male/female pairs were transferred to new maize grains for a week, then the adults were removed. The maize were kept for 7 weeks and the emerged adults were sieved off and counted (to give a measure of productivity), sexed and weighted. Emergence of adult weevils was higher when parents were previously kept on flour maize than when parents were previously kept on maize grain. The mean weight and the sex ratio (males/100 females) of the emerged adults did not differ between treatments. These results suggested that S. zeamais have plasticity and ability to successfully modify their oviposition behaviour to correspond to change in the experimental situation.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 3","pages":"511-7"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22342075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Susceptibility of four different vegetable brassicas to cabbage whitefly (Aleyrodes proletella L., Aleyrodidae) attack.","authors":"Stanislav Trdan,&nbsp;Ursa Papler","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Cabbage whitefly (Aleyrodes proletella L.) is one of the most noticeable pests on cultivated Brassica species in the continental part of Slovenia. In year 2000 a susceptibility of four different vegetables of Brassica genus to cabbage whitefly attack had been examined. The highest number of imagoes and larvae was found on kale, significantly less on savoy cabbage and Brussels sprouts and only individual specimen on cabbage. Due to relatively small parcels, the most appropriate way of determining potential economic importance was to count imogoes and larvae on plants (visual inspection). On the other hand, monitoring with sticky yellow boards gave less satisfactory results.</p>","PeriodicalId":85134,"journal":{"name":"Mededelingen (Rijksuniversiteit te Gent. Fakulteit van de Landbouwkundige en Toegepaste Biologische Wetenschappen)","volume":"67 3","pages":"531-5"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22342076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}