Fine-tuning banana Xanthomonas wilt control options over the past decade in East and Central Africa     

Guy Blomme  Kim Jacobsen  Walter Ocimati  Fen Beed  Jules Ntamwira  Charles Sivirihauma  Fred Ssekiwoko  Valentine Nakato  Jerome Kubiriba  Leena Tripathi  William Tinzaara  Flory Mbolela  Lambert Lutete  Eldad Karamura 《European journal of plant pathology / European Foundation for Plant Pathology》2014,139(2):265-281

Xanthomonas wilt, caused by Xanthomonas campestris pv. musacearum has, since 2001, become the most important and widespread disease of Musa in East and Central Africa. Over the past decade, new research findings and especially feedback from small-scale farmers have helped in fine-tuning Xanthomonas wilt control options. During the initial years of the Xanthomonas wilt epidemic in East Africa, the complete uprooting of diseased mats and the burning or burying of plant debris was advocated as part of a control package which included the use of clean garden tools and early removal of male buds to prevent insect vector transmission. Uprooting a complete mat (i.e. the mother plant and a varying number of lateral shoots) is understandably time-consuming and labour intensive and becomes very cumbersome when a large number of diseased mats have to be removed. Recent research findings suggest that Xcm bacteria do not colonize all lateral shoots (i.e. incomplete systemicity occurs) and even when present that this does not necessarily lead to symptom expression and disease. This led to a new control method whereby only the visibly diseased plants within a mat are cut at soil level. The underlying idea is that the continued removal of only the diseased plants in a field will reduce the inoculum level and will bring down disease incidence to an acceptable level. This method is less labour intensive and takes a short time compared to the removal of a complete mat. However, single diseased stem removal needs to go hand in hand with prevention of new infections that can occur through the use of contaminated garden tools or through insect vector transmission. Novel transgenic approaches are also discussed. This paper presents an overview of past and ongoing research towards the development of a more practical and less demanding control strategy for Xanthomonas wilt.  相似文献   

Trade-offs and synergies between ecosystem services in uneven-aged mountain forests: evidences using Pareto fronts     

Valentine Lafond  Thomas Cordonnier  Zhun Mao  Benoît Courbaud 《European Journal of Forest Research》2017,136(5-6):997-1012

Uneven-aged mountain forests are considered favourable for the continuous provisioning of multiple ecosystem services (ES). These ES may however exhibit trade-offs or synergies that can be modulated by forest management. Yet, our knowledge remains poor on both the relationships between ES and the way management practices can optimise and reconcile them. In this study, we aimed at (1) characterising trade-offs and synergies between timber production, biodiversity conservation and protection against natural hazards; (2) identifying efficient (i.e. Pareto-optimal) management scenarios for the joint provisioning of these ES; and (3) comparing them to “reference” management scenarios. Using a simulation framework that couples a forest dynamics model, a silviculture algorithm and linker functions relating ES indicators to stand structure, we predicted the response of different ES indicators to various uneven-aged management practices in the Western Alps. With a metamodeling approach and Pareto front techniques, we intensively explored and analysed relationships between ES indicators and found trade-offs between timber production and other ES, but synergies between protection and biodiversity. “Pareto-optimal” management scenarios were characterised by low thinning and harvesting intensities but exhibited gradients of total removals and deadwood and large tree retention along the Pareto front. They greatly differed from our set of production and biodiversity oriented reference scenarios, thus emphasising the strong impact of considering additional ES in scenario optimisation processes. This study highlighted the strengths and weaknesses of Pareto front techniques for both the analysis of trade-offs and synergies between ES and the identification of efficient management practices.  相似文献   

Changes in the population of germinated seed in a hill pasture during and after a pastoral fallow     

Nie  Barker  Valentine  Mackay  Hodgson 《Grass and Forage Science》1999,54(2):127-136

A pastoral fallow, which involves no defoliation of pasture for a period, generally from spring to autumn, is a management tool that can be used either to reduce plant population density through self-thinning prior to oversowing improved plant germplasm or to encourage natural reseeding in order to increase sward persistence and productivity. Two field experiments were carried out in a hill pasture in New Zealand to quantify the response of the seed population, germinated from soil plugs under glasshouse conditions for over 7 months, to pastoral fallow, as influenced by the timing and duration of the fallow, fertilizer application and aspect, and to identify the germination patterns of different plant species in fallowed and grazed swards. A spring–autumn pastoral fallow increased the germinated seed population of grasses, legumes and weeds by 161%, 51% and 59%, respectively, compared with the grazed control. The variation in germinated seed population during the pastoral fallow showed that seed quantity can be controlled by manipulating the timing and duration of a pastoral fallow. Short duration (2–3 month) pastoral fallows resulted in a significantly lower germinated grass seed population than the full (spring–autumn) fallows. Fertilizer application reduced the germinated grass seed population by 26%. The germinated legume seed population was higher with a shady than a sunny aspect. Regression analysis revealed that the germination patterns of all plant species followed a negative exponential function. Partial differentiation of this function derived a germination rate curve on which a two-pool (ephemeral pool and base pool) model was developed to describe quantitatively the dynamics of germinable seed reserves in the soil.  相似文献   

Brighter outlook for potatoes     

J. G. Lipman  H. O. Werner  E. P. Miller  Walter M. Peacock  Julian Dimock  R. F. Howard  R. G. Newton  Wm. H. Martin  George H. Valentine  Dee Crane  O. C. Hicks  H. C. Moore 《American Journal of Potato Research》1925,2(6):221-258

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Disease control and seed improvement number     

R. W. Goss  E. L. Newdick  George H. Valentine  H. O. Werner  D. R. Porter  J. M. Hurley  C. L. Fitch  W. H. Martin  Waiter M. Peacock 《American Journal of Potato Research》1925,2(7):261-294

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Compression characteristics of a clay soil as influenced by crops and sampling dates     

J. Lafond  D. A. Angers  M. R. Laverdi  re 《Soil & Tillage Research》1992,22(3-4):233-241

This study was undertaken to determine the influence of previous crop sequences on soil compression behaviour. Soil compression tests were performed on undisturbed soil samples of a Kamouraska clay which had been cropped continuously for 4 years to barley, corn, alfalfa, or timothy. Samples were taken from the surface soil in the non-trafficked zone, five times during the season. Cropping treatments had small but significant effects on soil compression characteristics. Soils on which crops were grown presented lower bulk density under standard compression (300 kPa) and higher pre-compression pressure values than the soil left unplanted (fallow). These effects were attributed to water content at time of sampling which was lower in the cropped than in the bare soils. Seasonal variations of these two virgin compression parameters were important and were related to soil moisture. Conversely, the soil compression index (slope of the virgin compression line) was not affected by crops or water content and seems to be a characteristic dependent on soil constituents.  相似文献   

Effects of tillage systems and rotations on crop production for a thin Black Chernozem in the Canadian Prairies   总被引：1，自引：0，他引：1  

G.P. Lafond  W.E. May  F.C. Stevenson  D.A. Derksen 《Soil & Tillage Research》2006,89(2):232-245

Soil degradation is the single most important threat to global food production and security. Wind and water erosion are the main forms of this degradation, and conservation tillage represents an effective method for controlling this problem. The objective of this study was to quantify the effects of three tillage methods [zero (ZT), minimum (MT) and conventional (CT)] and three four-year crop sequences [spring wheat (Triticum aestivum L.)–spring wheat–winter wheat–fallow; spring wheat–spring wheat–flax (Linum usitatissimum L.)–winter wheat; spring wheat–flax–winter wheat–field pea (Pisum sativum L.] on crop establishment, plant height, seed weight, soil water storage, crop water use, crop water use efficiency and grain yield over a 12-year period under Canadian growing conditions. Plant establishment was not adversely affected by tillage systems or crop sequences except for flax, where a small reduction was observed with ZT and MT. Conservation tillage showed a yield benefit over CT of 7%, 12.5% and 7.4% for field pea, flax and spring wheat grown on cereal stubble, respectively over the 12 years of the study. Much of the yield increase was due to an increase in soil water in the 0–30 cm soil layer with ZT and MT. However, tillage systems had no effect on grain yield for spring wheat grown on fallow and field pea stubble due to a lack of differences in spring soil water content. Flax grown in sequence with cereals only yielded higher than when it was grown in the sequence which included field pea, even though flax was seeded on spring wheat stubble in both cases. Winter wheat yielded higher when grown on flax stubble than on spring wheat stubble. The results indicate that a one-year non-cereal break crop was enough to alleviate the negative effects of consecutive cereal crops on winter wheat. Spring wheat grown on field pea stubble always yielded more than when grown on cereal stubble. A 10% increase in water use efficiency was observed with flax grown with ZT and MT management. Crop sequence improved water use efficiency in flax and spring wheat. Growing spring wheat on field pea stubble as opposed to growing it on cereal stubble resulted in a 10% increase in water use efficiency. Overall, rainfall accounted for 73%, 72%, 67% and 65% of total water used by field pea, flax, winter wheat and spring wheat, respectively. This explains the large year effect as a result of variation in growing (May–August) season precipitation. The non-significant tillage system by year interaction implies that the positive benefits of ZT and MT occur over a wide range of growing conditions, while the absence of a tillage system by crop sequence interaction suggests that knowledge developed under CT management also applies to ZT and MT. The results of this study support the large shifts towards in conservation tillage being observed in the Canadian prairies.  相似文献   

Canine Congenital Diaphragmatic Hernia     

Beth A. Valentine DVM  Barry J. Cooper BVSc  PhD    Amy E. Dietze DVM  Drew M. Noden PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1988,2(3):109-112

Congenital diaphragmatic hernia, affecting both sexes, was present in five of 27 puppies from three father-daughter matings. A purebred Golden Retriever was the common sire. The defect occurred in the left dorsolateral portion of the diaphragm, suggesting failure of closure of the left pleuroperitoneal canal during embryonic development. These findings, and a previous report of a similar defect in neonatal puppies, are consistent with autosomal recessive inheritance of canine diaphragmatic defects.  相似文献   

Metastatic testicular embryonal carcinoma in a horse   总被引：1，自引：0，他引：1  

B A Valentine  D Weinstock 《Veterinary pathology》1986,23(1):92-96

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Naked oats: metabolisable energy yield from a range of varieties in broilers, cockerels and turkeys     

MacLeod MG  McNeill L  Bernard K  Valentine J  Wade A 《British poultry science》2004,45(Z1):S19-S20

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