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Plant Substrate (plant + substrate)
Selected AbstractsThe influence of greenhouse chrysanthemum on the interaction between the beet armyworm, Spodoptera exigua, and the baculovirus SeMNPV: parameter quantification for a process-based simulation modelJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001F. J. J. A. Bianchi During the building of a process-based simulation model for the epidemiology of the multicapsid nucleopolyhedrovirus of S. exigua (SeMNPV) in populations of Spodoptera exigua (Hübner) in greenhouse chrysanthemum, it was found that the effect of host plants had been under-rated. ,Missing links' included (i) the ,natural' background mortality of larvae of S. exigua in practical cropping conditions; (ii) the developmental rate of larvae of S. exigua on plant substrate in a glasshouse as compared to artificial medium in the laboratory; (iii) the validity of the results of dose-mortality and time-mortality bioassays conducted on artificial medium as compared to natural plant substrate; (iv) the distribution of inoculum released from deceased caterpillars over chrysanthemum leaves; and (v) the leaf visit rate of healthy caterpillars (as it affects horizontal transmission). Experiments were carried out to quantify these processes. Developmental rates of S. exigua larvae on greenhouse chrysanthemum were 36% lower than on an artificial diet. The fraction survival during the first, second, third and fourth instar S. exigua larvae in greenhouse chrysanthemum was 0.60, 0.80, 0.88 and 0.95, respectively. Forty percent of the first instar larvae reached the fifth larval stage. Second instar S. exigua larvae reared on chrysanthemum were significantly more susceptible to SeMNPV than larvae reared on an artificial diet. The food source had no effect on the time to kill S. exigua larvae. Cadavers of second, third and fourth instar S. exigua larvae contaminated on average 1.4, 2.5 and 3.3 chrysanthemum leaves. Second to fourth instar S. exigua larvae visited 2,3 leaves per day and spent 15,55% of the time on the underside of leaves. The above information is of critical importance for a trustworthy simulation of the epidemiology of SeMNPV in chrysanthemum. [source] Dairy cows trapped between performance demands and adaptability,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2009Wilhelm Knaus Abstract The tremendous increase in the lactation performance of dairy cows during the last 60 years has had dramatic consequences on fertility and vitality (fitness) of the animals. Unprecedented average lactation performance levels have resulted in an equally unprecedented reduction in longevity. Economic pressure to further reduce the age at first calving is still high, although the negative correlation between precocious maturity and longevity is well documented in the relevant literature. Ever more aggressive selection and feeding measures are being taken to shorten the rearing time of heifers in order to reduce the cost of replacement heifers. An additional decrease in the stayability of cows has to be expected when the age at first calving is lowered even further. For reasons of profitability, dairy cows should complete an average of at least four lactations. Cows from the most important dairy breeds in the United States and Bavaria, Germany, already dropped below that crucial threshold many years ago. The same phenomenon has been observed in dairy cows in Austria over the past few years. Holstein cows that were culled in Austria in 2007 had an average of only 3.3 parities. To improve this situation, dairy cattle breeding programs should put a much higher emphasis on selection for traits of longevity and lifetime performance and, in return, markedly reduce the emphasis on selection for lactation performance in general and early-lactation performance test results in particular. Over millions of years of evolutionary adaptation, cattle have acquired the ability to utilize fibrous low-quality plant substrate. Only a strongly forage-based feeding regimen is, in the long run, in accordance with their digestive and metabolic configuration. The massive use of concentrates (mostly grain) in cattle rations increases the risk of digestive and metabolic disorders in cattle and consequently leads to impaired animal welfare. Finally, the careful management of scarce resources demands that a closer look be taken at the food balance in dairy rations, i.e., an awareness of how much food that is edible for humans is being fed to livestock. Copyright © 2009 Society of Chemical Industry [source] Validation of a real-time PCR method for the detection of Phytophthora ramorum1EPPO BULLETIN, Issue 2 2006A. Chandelier To validate a real-time PCR method for the detection of Phytophthora ramorum, an intra-laboratory procedure was developed. The specificity of the TaqMan probe/primer sets was determined by carrying out real-time PCR on total DNA extracted from pure culture of several Phytophthora species. The limit of detection and the potential effects of plant substrates were evaluated by conducting the test on total DNA from healthy plant materials (Rhododendron spp., Viburnum spp. and Pieris spp.) spiked with known amounts of P. ramorum genomic DNA. The PCR efficiency was estimated through the linear regression of the dilution curve. Precision of the TaqMan assay was assessed on material from a single artificially infected plant (Rhododendron spp.). Two kinds of tissues were tested: a severely infected twig and an apparently healthy leaf. Intra-assay repeatability was evaluated on 10 replicates of the same DNA sample analysed in a single assay. Inter-assay reproducibility was evaluated on the same DNA sample amplified over five separate assays while the intersample reproducibility was evaluated on separate DNA extractions of four samples from both plant tissues amplified in a single assay. [source] Trichoderma enzymes promote Fibrobacter succinogenes S85 adhesion to, and degradation of, complex substrates but not pure cellulose,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2004Diego P Morgavi Abstract The effects of an enzyme preparation from Trichoderma longibrachiatum (TE) on adhesion and growth of the fibrolytic rumen bacterium Fibrobacter succinogenes S85 was studied to gain a better understanding of the action of feed enzyme additives on fibre digestion by ruminants. Adhesion experiments were performed on crystalline cellulose, corn silage and alfalfa hay. Adhesion of F succinogenes to cellulose was negatively related to the concentration of TE (p < 0.05). At the highest concentration used, TE reduced adhesion to cellulose from 65 to 39%. For corn silage and alfalfa hay, TE stimulated adhesion at low levels (p < 0.05) but this effect was lost at higher levels. Culture experiments were performed on crystalline cellulose and corn silage. The presence of TE in media containing cellulose failed to increase substrate disappearance or gas production although it increased numbers of non-adherent bacteria (p < 0.05). When corn silage was used, the addition of TE increased NDF disappearance (p < 0.05) at 24 and 48 h (33 and 52% in controls versus 53 and 65% in TE treatments). Growth rate and gas production were also stimulated (p < 0.05). We conclude that, for cellulose, the hydrolytic enzymes in TE obstructed available binding sites decreasing bacterial adherence. Fibrobacter succinogenes digested cellulose efficiently and addition of exogenous cellulases did not further increase substrate disappearance. However, for complex plant substrates, low concentration of TE increased bacterial adhesion and plant (corn) fiber degradation. For the Department of Agriculture and Agri-Food, Government of Canada, © Minister of Public Works and Government Services Canada 2004. Published for SCI by John Wiley & Sons, Ltd. 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