Forecasting Crop Damage by Nematodes: Nematode Population Dynamics¹     

F.G.W. JONES  R.A. KEMPTON 《EPPO Bulletin》1980,10(2):169-180

Factors affecting the ease or difficulty of forecasting and modelling cyst, root-ectoparasitic and soil surface nematodes are mentioned. To relate pre-planting to post-harvest populations of cyst nematodes, a version of the logistic curve is derived from first principles and modified to take account of the injury done to root systems as numbers increase, and of eggs carried over to the following year. Egg hatch, when potato or other crops are grown, appears to be independent of population density. So also does root invasion over the population densities encountered in field plots. In the absence of enemies, population density is determined by competition for feeding sites induced by females in the root system, and by the size of the root system. Population oscillations about the equilibrium point are affected mainly by the proportion of the population that fails to hatch and the damage to the root system. The process of model building and the parameters required are outlined. The model includes hypotheses relating to intraspecific (genetic) competition and interspecific competition. The limitations of models and the need to make them stochastic are discussed. L'article fait état des possibilites et difficultés rencontrees dam la prévision et la modelisation des populations de nematodes a kystes, de nematodes ectoparasites des racines, et de nematodes de surface. Afin detablir la relation entre les populations de nematodes a kystes avant le semis et apres la recolte, il est recouru a la courbe logistique, derivee des principes fondamentaux. Celle-ci se trouve modifiee afin de tenir compte des degits croissants subis par les racines en fonction de I'augmentation des populations et de la survie d'une partie des ceufs d'une annee a I'autre. L'eclosion des ceufs semble être independante de la densite des populations dans les champs de pommes de terre et de toute autre culture. Ceci s'applique egalement a I'invasion des racines, dans le cas des densites de populations observees dans les parcelles experimentales. En I'absence dennemis, la densite est determinee par la competition pour L'acces aux sites de nutrition que les femelles preparent dans les racines, et par L'importance du systeme radiculaire. Les ecarts de population observes a partir dun equilibre sont principalement dus a la proportion de la population non eclose et aux deggts subis par les racines. I1 est fait etat d'une modelisation, basee sur certains parametres essentiels. Le modele repose sur L'hypothese d'une concurrence intraspecifique (genetique) et interspecifique. Les limites des modeles sont considerees, ainsi que la necessite de passer a une approche stochastique.  相似文献   

Production of Lambs After the Transfer of Fresh and Cryopreserved in vitro Produced Embryos from Prepubertal Lamb Oocytes and Unsorted and Sex-sorted Frozen-thawed Spermatozoa     

KM Morton  SL Catt  FK Hollinshead  WMC Maxwell  G Evans 《Reproduction in domestic animals》2004,39(6):454-461

Cumulus-oocyte complexes from hormone-stimulated 3-4-week-old (n=43) and 6-7-week-old (n=12) prepubertal lambs were matured in vitro and incubated with unsorted, or X- or Y-spermatozoa separated with a high-speed cell sorter (SX MoFlo)frozen-thawed. Presumptive zygotes were then cultured to the blastocyst stage, and transferred to recipients fresh or after cryopreservation (frozen). Oocyte cleavage was higher (p <0.05) with unsorted (515/926, 55.6%) than X- or Y-spermatozoa (261/672, 38.8% and 229/651, 35.2%, respectively) and blastocyst formation (% zygotes) by Day 9 of in vitro culture was lower (p <0.05) for X- (102/261, 39.1%) than unsorted spermatozoa (249/515, 48.3%), but did not differ between Y-spermatozoa (103/229, 45.0%) and unsorted spermatozoa, or between X- and Y-spermatozoa (p >0.05). For fresh embryos, survival to term was 50.0% (3/6) for unsorted, 0.0% (0/6) for X- and 16.7% (1/6) for Y-spermatozoa-derived embryos (p >0.05), and for frozen embryos was 4.0% (2/50) for unsorted, 9.1% (2/22) for X- and 2.9% (1/34) Y-spermatozoa-derived embryos (p >0.05). Of the two lambs born from X-spermatozoa-derived embryos, one was female (50%), and from the two Y-spermatozoa-derived lambs, both were male (100%), demonstrating that lambs can be produced after the transfer of fresh and cryopreserved IVP embryos derived from prepubertal lamb oocytes and frozen-thawed sex-sorted sperm.  相似文献   

Comparison of responses to floret and seedling inoculation in wheat- Ustilago tritici and barley- U. nuda combinations     

P. JONES  P. DHITAPHICHIT 《Plant pathology》1991,40(2):268-277

The floret and seedling methods for inoculating wheat and barley with Ustilago tritici and U. nuda, respectively, were optimized and then compared. Floret inoculation gave higher infection levels than did seedling inoculation, especially for wheat, but problems of plant mortality and standardization of tissue age were greater with the former method. Floret inoculation identified wheat and barley varieties exhibiting embryo resistance (class 1 or 2 resistance) or seedling resistance (class 3), but only class 3 wheat and barley varieties (and one class 2 wheat variety) were resistant to seedling inoculation. Using near-isogenic wheat lines expressing different levels of partial resistance to floret inoculation, positive correlations were obtained between percentage infection levels resulting from the two inoculation protocols. In addition, race-specific host-pathogen interactions such as hypersensitivity and partial smutting were expressed following both floret and seedling inoculation, indicating that these interactions operate in the developing plant. The potential value of the seedling inoculation method in fundamental and applied research into the cereal-loose smut interaction is discussed.  相似文献   

Problems associated with potyviruses in potato certification-field inspection and serological testing1     

R. A. C. JONES 《EPPO Bulletin》1987,17(1):61-67

In UK, the tobacco veinal necrosis strain of potato virus Y (PVY^N), potato virus A (PVA) and potato virus V (PVV) each occur in the field only in limited ranges of potato cultivars in which they mostly cause mild symptoms or even symptomless infection; little is known about incidence of strain C of PVY (PVY^C). The ordinary strain of PVY (PVY°), however, is widespread causing symptoms ranging in severity from very severe through to very mild, depending on cultivar sensitivity/tolerance. During field inspections, very mild potyvirus symptoms may be missed, so inspectors are trained to be particularly vigilant when examining problem cultivars which react in this way. PVA is almost invariably treated, along with PVX, as a mild kind of virus infection, but infections with PVY°, PVY^N and PVV are treated as severe with stricter tolerances being applied for them (especially for PVY^N) regardless of symptom severity. Wide variation within the same cultivar in the behaviour of variants within the PVY° strain group also sometimes causes difficulties in interpretation at inspection. To detect PVY, PVA and PVV in routine serological testing on potato certification samples, it is necessary to employ specific antisera to each of them. PVY^N-specific monoclonal antibodies can be used in ELISA to distinguish PVY^N from PVY°.  相似文献   

Causes of preweaning mortality on a large intensive piggery     

E M SPICER  S J DRIESEN  V A FAHY  B J HORTON  L D SIMS  R T JONES  R S CUTLER  R W PRIME 《Australian veterinary journal》1986,63(3):71-75

Causes of preweaning mortality were examined on a large intensive piggery. Diagnosis was made using comprehensive clinical histories combined with post-mortem data. Two thousand four hundred and twenty-six piglets were born in 238 litters. Pre-parturient and parturient losses were 2.9% and 5.4% of the total numbers of piglets born. Birth to weaning mortality was 11.3%. Among piglets born alive, overlaying was the most frequent cause of death (2.1%), followed by deaths due to diarrhoea (1.7%), anaemia (1.2%), savaging (1.1%) and losses of small weak piglets (0.9%). Most deaths, including stillbirths, were associated with below average birth weight, and two-thirds of all deaths of liveborn pigs occurred within 4 days of birth. Increased litter size resulted in decreased birth weights, an increased percentage of stillborn piglets and mummified foetuses, but duration of parturition was not affected. Stillborn piglets were born late in the litter and after a longer interval between pigs born (interpig interval). Over 70% of deaths due to overlay were in previously healthy piglets, but some were associated with illness of the sow (18%) or both sow and piglet (3%). Savaging was confined mainly to first parity sows and was responsible for 20% of all deaths in these litters. Sixty-two per cent of all piglets with a birth weight of less than 800g were stillborn or died before weaning compared with 18.7% mortality for all piglets. Anaemia in piglets was considered to be due to umbilical haemorrhage. Anaemic piglets had a 36% mortality to weaning compared with 10% for non-anaemic piglets.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

MYELOMALACIA IN AFGHAN HOUNDS     

B. R. JONES  R. B. RICHARDS 《Australian veterinary journal》1977,53(9):452-453

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The effect of drying techniques on formononetin concentration in red clover     

R. JONES 《Grass and Forage Science》1979,34(3):233-236

Oven-drying at 60°, 80° or 105°C was compared with microwave and freeze-drying as a method of preparing samples for the estimation of formononetin, the major oestrogenic factor in red clover. There was no significant difference in the formononetin concentration of clover samples either oven-dried at 60°C or freeze-dried. The formononetin concentration was reduced by drying at higher temperatures and by microwave-drying but was not affected by wilting for up to 8 h after harvesting. The routine determination of formononetin in ten varieties of red clover showed no significant differences between samples cold stored at – 18°C prior to oven-drying at 60°C and samples freeze-dried.  相似文献   

Editorial     

J. G. W. JONES 《Grass and Forage Science》1978,33(1):1-1

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The effect of seed pretreatment and sowing date on the nursery emergence of Sitka spruce (Picea sitchensis [Bong.] Carr.) seedlings     

JINKS  R. L.; JONES  S. K. 《Forestry》1996,69(4):335-345

Sitka spruce seeds which had been: (1) untreated (U), (2) prechilled(P), or (3) prechilled and then redried and stored for 16 months(R), were sown into progressively warmer seed beds on four datesat monthly intervals from March to June. At each sowing date,samples of seed were germinated in the laboratory at optimum(20°C) and sub-optimum (10°C) temperatures. Prechillingand prechilling + redrying both increased the rate and totalamount of germination compared with untreated seed at each testtemperature. However in the nursery, the beneficial effectsof pretreating Sitka spruce seed were restricted to sowing inMarch and April when soil temperatures were sub-optimal forthe germination of untreated seeds. Pretreatment resulted inrapid seedling emergence at soil temperatures between 10°Cand 15°C, whereas untreated seed germinated slowly and seedlingemergence continued until high soil temperatures in June killedungerminated seeds. The pattern of seedling emergence from theredried seed was similar to that from the prechilled seed, exceptfor a lag in the start of seedling emergence probably due tothe extra time needed for redried seed to imbibe water in theseed beds. Thus redrying caused insignificant loss of seed performanceon the nursery. Seed sown in May and June experienced average temperatures closeto the optimum for germination of 20°C, however daily maximaregularly exceeded 35°C resulting in the cessation of seedlingemergence in all three seed treatments, and the loss of newlyemerged seedlings. Periods of warm weather from June onwardswere the main factors limiting the final number and size ofseedlings.  相似文献   

THE STORAGE OF ACORNS IN WATER     

JONES  EUSTACE W. 《Forestry》1958,31(2):163-166

Acorns of sessile oak (Quercus petraea) will not tolerate prolongedsubmergence, but those of pedunculate oak (Quercus robur) survivevery well in regularly changed distilled water or tap-water.Survival is considerably worse in basic river water; the differencefrom tap-water is likely to be due either to the greater activityof organisms promoting decay, or to the prevalence of loweroxygen-tensions in river water. Storage in water under suitablycontrolled conditions might be a useful practical procedurewith pedunculate acorns.  相似文献