971 resultados para Alfalfa seedling bioassay


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Dormancy is an adaptive trait in seed populations that helps ensure that seed germination is distributed over time and occurs in environmental conditions suitable for seedling growth. Several genes.. associated with seed dormancy in various plant species, have been integrated into a hypothetical dormancy model for Avena fatua L. (wild oats). Generally, the synthesis of, and sensitivity to, abscisic acid (ABA) during imbibition determines whether genes similar to those during maturation are expressed leading to a maintenance of dormancy during extended imbibition. Alternatively, there may be a shift towards expression of genes associated with gibberellins leading to germination. Environmental factors during maturation, after-ripening and imbibition are likely to interact with the genotype to affect gene expression and hence whether or not a seed germinates. In spite of the difficulties of working on a hexaploid species, A. fatua was selected for study because of its worldwide importance as a weed. Dormant and non-dormant genotypes of this species were also available. Gene expression studies are being carried out on three A.fatua genotypes produced tinder different environmental conditions to investigate the role of specific genes in dormancy and genotype X environment interactions in relation to dormancy.

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The influence, was investigated, of abiotic parameters on the isolation of protoplasts from in vitro seedling cotyledons of white lupin. The protoplasts were found to be competent in withstanding a wide range of osmotic potentials of the enzyme medium, however, -2.25 MPa (0.5 M mannitol), resulted in the highest yield of protoplasts. The pH of the isolation medium also had a profound effect on protoplast production. Vacuum infiltration of the enzyme solution into the cotyledon tissue resulted in a progressive drop in the yield of protoplasts. The speed and duration of orbital agitation of the cotyledon tissue played a significant role in the release of protoplasts and a two step (stationary-gyratory) regime was found to be better than the gyratory-only system.

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Screenhouse experiments conducted in Kenya showed that inoculation of cabbage seedlings with Turnip mosaic virus (TuMV), either alone, or in combination with Cauliflower mosaic virus (CaMV), reduced the number and weight of marketable harvested heads. When viruses were inoculated simultaneously, 25% of cabbage heads were non-marketable, representing 20-fold loss compared with control. By contrast, inoculation with CaMV alone had insignificant effects on cabbage yield. This suggests that TuMV is the more detrimental of these pathogens, and its management should be a priority. Early exposure to TuMV produced cabbages that were 50% lighter than non-infected plants, but later infection was less damaging suggesting that controlling virus infection at the seedling stage is more important. TuMV was far less damaging to kale than it was to cabbage; although high proportions of TuMV-inoculated kale plants showed symptoms (> 90%), the marketability and quality of leaves were not significantly reduced, and no clear relationship existed between timing of infection and subsequent crop losses. Early inoculation of Swiss chard with Beet mosaic virus (BtMV) significantly impaired leaf quality (similar to 50% reduction in marketable leaf production), but the impact of disease was greatest in plants that had been inoculated at maturity, where average leaf losses were two and a half times those recorded in virus-free plants. Disease-management of BtMV in Swiss chard is important, therefore, not only at the seedling stage, but particularly when plants are transplanted from nursery to field.

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Milk supply from Mexican dairy farms does not meet demand and small-scale farms can contribute toward closing the gap. Two multi-criteria programming techniques, goal programming and compromise programming, were used in a study of small-scale dairy farms in central Mexico. To build the goal and compromise programming models, 4 ordinary linear programming models were also developed, which had objective functions to maximize metabolizable energy for milk production, to maximize margin of income over feed costs, to maximize metabolizable protein for milk production, and to minimize purchased feedstuffs. Neither multicriteria approach was significantly better than the other; however, by applying both models it was possible to perform a more comprehensive analysis of these small-scale dairy systems. The multi-criteria programming models affirm findings from previous work and suggest that a forage strategy based on alfalfa, rye-grass, and corn silage would meet nutrient requirements of the herd. Both models suggested that there is an economic advantage in rescheduling the calving season to the second and third calendar quarters to better synchronize higher demand for nutrients with the period of high forage availability.

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Small-scale dairy systems play an important role in the Mexican dairy sector and farm planning activities related to resource allocation have a significant impact on the profitability of such enterprises. Linear programming is a technique widely used for planning and ration formulation, and partial budgeting is a technique for assessing the impact of changes on the profitability of an enterprise. This study used both methods to optimise land use for forage production and nutrient availability, and to evaluate the economic impact of such changes in small-scale Mexican dairy systems. The model showed satisfactory performance when optimal solutions were compared with the traditional strategy. The strategy using fresh ryegrass, maize silage and oat hay, and the strategy using a combination of alfalfa hay, maize silage, fresh ryegrass and oat hay appeared attractive options for providing a better nutrient supply and maintaining a higher stocking rate throughout the year than the traditional strategy.

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Two trials were conducted to evaluate effects of feeding supplemental fibrolytic enzymes or soluble sugars and malic acid on milk production. In trial 1, 257 cows at four sites were fed a basal diet consisting of no more than 60% of forage DM as corn silage and less than 40% as alfalfa hay. Cows were assigned randomly within site, parity, and two stages of lactation to: 1) control; 2) enzyme A; 3) enzyme B; and 4) soluble sugars and malic acid. There was a 14-d pretreatment and an 84-d treatment period. Enzyme solutions were sprayed on either the forage component or the TMR each day while mixing feed. Trial 2 was similar, except 122 cows at one site in the United Kingdom were fed diets containing forage that was 75% corn silage and 25% grass silage, and all cows began the study between 25 to 31 DIM. Mean milk productions for 233 cows that completed trial 1 were 32.9, 32.5, 32.4, and 32.9 kg/d for control, enzyme A, enzyme B, and soluble sugars and malic acid, respectively. Mean milk productions for 116 cows that completed trial 2 were 28.2, 27.9, 28.8, and 28.4 kg/d, respectively. In vitro analyses of the activities of enzyme solutions indicated that all major cellulose and hemicellulose degrading activities were present; however, the pH optima (approximate pH = 4 to 5) were more acidic, and the temperature optimum (approximately 50 C) was greater than normal pH and temperature in the rumen. If fibrolytic activity in the rumen is a major mechanism of action of supplemental fibrolytic enzymes, it appears that considerable activity of these preparations was lost due to conditions in the rumen. In conclusion, feeding supplemental fibrolytic enzymes or malic acid with soluble sugars had no effect on milk production under the conditions used in this study.

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The management of straw residue can be a concern in non-inversion tillage systems where straw tends to be incorporated at shallow depths or left on the soil surface. This can lead to poor crop establishment because straw residue can impede or hinder crop emergence and growth. Small container-based experiments were undertaken using varying amounts of wheat straw residue either incorporated or placed oil the soil surface. The effects on (lays to seedling emergence, percentage emergence, seedling dry-weight and soil temperature using sugar beet and oilseed rape were investigated because these crops often follow wheat in a cropping sequence. The position of the straw residue was found to be the primary factor in reducing crop emergence and growth. Increasing the amount of straw residue (from 3.3 t ha(-1) to 6.7 t ha(-1)) did not show any consistent trends in reducing crop emergence or growth. However, in some instances, results indicated that an interaction between the position and the amount of straw residue Occurred particularly when the straw and seed was placed on the soil surface. Straw placed on the soil surface significantly reduced mean day-time soil temperature by approximately 2.5 degrees C compared to no residue. When the seed and straw was placed on the soil Surface a lack of seed-to-soil contact caused a reduction in emergence by approximately 30% because of the restriction in available moisture that limited the ability for seed imbibition. This trend was reversed when the seed was placed in the soil, but with straw residue still on the soil surface, because the surface straw was likely to reduce moisture evaporation and improved seed-to-soil contact that led to rapid emergence. In general, when straw was mixed in or placed on the soil surface along with the seed, sugar beet and oilseed rape emergence and early growth biomass was significantly restricted by approximately 50% compared to no residue. The consequences of placing seed with or near to straw residue have been shown to cause a restriction in crop establishment. In both oilseed tape and sugar beet, this could lead to a reduction in final crop densities, poor, uneven growth and potentially lower yields that could lower financial margins. Therefore, if farmers are planning to use non-inversion tillage methods for crop establishment, the management and removal of straw residue from near or above the seed is considered important for successful crop establishment. (C) 2008 Elsevier B.V. All rights reserved.

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A detached leaf bioassay was used to determine the influence of several film forming polymers and a conventional triazole fungicide on apple scab (Venturia inaequalis (Cooke) G. Wint.) development under laboratory in vitro conditions, supported by two field trials using established apple cv. Golden Delicious to further assess the efficacy of foliar applied film forming polymers as scab protectant compounds. All film forming polymers used in this investigation (Bond, Designer, Nu-Film P, Spray Gard, Moisturin, Companion PCT12) inhibited germination of conidia, subsequent formation of appressoria and reduced leaf scab severity using a detached leaf bioassay. Regardless of treatment, there were no obvious trends in the percentage of conidia with one to four appressoria 5 days after inoculation. The synthetic fungicide penconazole resulted in the greatest levels of germination inhibition, appressorium development and least leaf scab severity. Under field conditions, scab severity on leaves and fruit of apple cv. Golden Delicious treated with a film forming polymer (Bond, Spray Gard, Moisturin) was less than on untreated controls. However, greatest protection in both field trials was provided by the synthetic fungicide penconazole. Higher chlorophyll fluorescence Fv/Fm emissions in polymer and penconazole treated trees indicated less damage to the leaf photosynthetic system as a result of fungal invasion. In addition, higher SPAD values as measures of leaf chlorophyll content were recorded in polymer and penconazole treated trees. Application of a film forming polymer or penconazole resulted in a higher apple yield per tree at harvest in both the 2005 and 2006 field trials compared to untreated controls. Results suggest application of an appropriate film forming polymer may provide a useful addition to existing methods of apple scab management. (C) 2008 Elsevier Ltd. All rights reserved.

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Six nutrient formulations were studied for their efficacy in inducing mitosis in white lupin seedling cotyledon protoplasts of which the formulations of Schafer-Menuhr & Sturmer (AS) and Kao (K8p) were found to be superior over the other four when supplemented with 6-benzylaminopurine and alpha-naphthaleneacetic acid (alpha-NAA). An unltrafiltration treatment of K8p increased mitotic frequency by 130% when compared with the untreated control. Medium enrichment with 0.2% bovine serum albumin (BSA) brought about a dramatic 1341% rise in protoplast division in comparison with BSA-free medium but only when the enrichment was carried out in Kao and Michayluk (KM8p) background containing 2, 4-dichlorophenoxyacetic acid, alpha-NAA and zeatin. A higher number of protocolonies (each proliferating from single protoplast following multiple divisions) were seen in 0.4% BSA. With this breakthrough in white lupin protoplast research, it is now possible to reproducibly obtain protocolonies that was hitherto not possible.

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Transmission properties of Iranian wheat stripe virus (IWSV), a tentative member of the genus Tenuivirus, were studied. Results showed that similar to other tenuiviruses, IWSV multiplies in its vector, Unkanodes tanasijevici. In bioassay experiments, IWSV transmission rate by individual U. tanasijevici showed an increase with time after acquisition. IWSV was transovarially transmitted to 88-100% of progeny. The nymphs continued to be infective in the adult stage but with decreased efficiency. Males and females transmitted the virus with equal efficiency. Transmission properties of IWSV confirm the position of the virus in the genus Tenuivirus.

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The importance of dispersal for the maintenance of biodiversity, while long-recognized, has remained unresolved. We used molecular markers to measure effective dispersal in a natural population of the vertebrate-dispersed Neotropical tree, Simarouba amara (Simaroubaceae) by comparing the distances between maternal parents and their offspring and comparing gene movement via seed and pollen in the 50 ha plot of the Barro Colorado Island forest, Central Panama. In all cases (parent-pair, mother-offspring, father-offspring, sib-sib) distances between related pairs were significantly greater than distances to nearest possible neighbours within each category. Long-distance seedling establishment was frequent: 74% of assigned seedlings established > 100 m from the maternal parent [mean = 392 +/- 234.6 m (SD), range = 9.3-1000.5 m] and pollen-mediated gene flow was comparable to that of seed [mean = 345.0 +/- 157.7 m (SD), range 57.6-739.7 m]. For S. amara we found approximately a 10-fold difference between distances estimated by inverse modelling and mean seedling recruitment distances (39 m vs. 392 m). Our findings have important implications for future studies in forest demography and regeneration, with most seedlings establishing at distances far exceeding those demonstrated by negative density-dependent effects.

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This study reports on the influence of critical isolation factors on the subsequent culture of protoplasts of Lupinus albus L. Protoplasts were isolated from in vitro seedling cotyledons of five early maturing accessions in which protoplast yields and division frequencies appeared to be correlated as a high protoplast yield corresponded with a high division frequency. The overall difference among the accessions for mitosis was non- significant, although the highest yield and division frequency were observed in accession LA132, with Alban giving a significantly lower level. Accession Lucrop produced the lowest number of protoplasts, all of which collapsed during culture. Of the enzyme types used for tissue maceration, Pectolyase Y23, was significantly inferior to Macerase in terms of giving way to mitosis. The extent of division in Macerase- isolated protoplast population was 266% higher than that in the Pectolyase Y23- isolated one. The physiological maturity level of the explant, expressed in terms of developmental age, was optimal when 14 - 18- day- old seedling cotyledons were used for protoplast production and culture, rather than more mature ones, despite higher protoplast yields in the latter. On K8p medium, the protoplast division frequency was 129% greater when 18- day- old seedling cotyledons were used, than that with any other treatment. This work on protoplast culture of the potentially important lupin species, which is a pulse rich in dietary protein, oil and fibre, allows a further understanding of the biology, with an aim to advance lupin biotechnology.

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This study was designed to test the feasibility of integrating in situ, single species exposures and biomarker analysis into microcosm studies. Experimental ponds were dosed with pirimiphos methyl (PM) and lindane. C. riparius fourth instar larvae were deployed for 48 h on nine separate occasions during the study period before and after treatment. Surviving larvae were analysed for acetylcholinesterase activity (AChE). Survival and biomarker data were compared to chironomid assemblage analysis by monitoring insects emerging from the microcosms. Survival of chironomids within the in situ systems commenced on day + 16 after treatment with 31.6% and 53.3% survival in the lindane and PM treated ponds, respectively. In contrast, the first emergence from the microcosms occurred on days + 27, in respect to lindane, and + 59 for the PM treated ponds. Thus the in situ bioassay was able to demonstrate gradual reduction in toxicity within the sediment before this was evident from macroinvertebrate monitoring. Significant ACNE inhibition was only detected on exposure to PM. Levels decreased from 75% on day + 16 to 26% by day +29. The biomarker analysis confirmed that, by the end of the study, the insecticide was no longer exerting an effect. We discuss how the use of in situ bioassays could also aid comparison of microcosm studies by adding a standardized dimension. (C) 2003 Elsevier Ltd. All rights reserved.

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Part IIA of the Environmental Protection Act 1990 requires environmental regulators to assess the risk of contaminants leaching from soils into groundwater (DETR, 1999). This newly introduced legislation assumes a link between soil and groundwater chemistry, in which rainwater leaches contaminants from soil into the saturated zone. As the toxicity of both groundwater and overlying soils is dependent upon the chemicals present, their partitioning and their bioavailability, similar patterns of soil, leachates and groundwater toxicity should be observed at contaminated sites. Soil and groundwater samples were collected from different contaminated land sites in an urban area, and used to determine relationships between soil chemistry and toxicity, mobility of contaminants, and groundwater chemistry and toxicity. Soils were leached using water to mimic rainfall, and both the soils and leachates tested using bioassays. Soil bioassays were carried out using Eisenia fetida, whilst groundwater and leachates were tested using the Microtox(TM) test system and Daphnia magna 48 h acute tests. Analysis of the bioassay responses demonstrated that a number of the samples were toxic to test organisms, however, there were no significant statistical relationships between soil, groundwater and leachate toxicity. Nor were there significant correlations between soil, leachates and groundwater chemistry.

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The influence, was investigated, of abiotic parameters on the isolation of protoplasts from in vitro seedling cotyledons of white lupin. The protoplasts were found to be competent in withstanding a wide range of osmotic potentials of the enzyme medium, however, −2.25 MPa (0.5 M mannitol), resulted in the highest yield of protoplasts. The pH of the isolation medium also had a profound effect on protoplast production. Vacuum infiltration of the enzyme solution into the cotyledon tissue resulted in a progressive drop in the yield of protoplasts. The speed and duration of orbital agitation of the cotyledon tissue played a significant role in the release of protoplasts and a two step (stationary-gyratory) regime was found to be better than the gyratory-only system.