Root-knot nematodes (RKN) are major pest of olive tree (Olea europaea ssp. europaea), especially in nurseries and high-density orchards. Soil samples were collected from main olive growing areas of Morocco, to characterize Meloidogyne species and to discuss the contribution of biotic and abiotic factors in their spatial distribution.
Results
RKN were found in 159 soil samples out of 305 from nurseries (52.1% occurrence) and in 11 out of 49 soil samples from orchards (23.2% occurrence). Biochemical and molecular characterisation (PAGE esterase and SCAR) revealed the dominance of M. javanica both in nurseries and orchards with minor presence of M. incognita only in nurseries, and M. arenaria in only one nursery. RKN were distributed on aggregated basis. Frequent presence of M. javanica in orchards might have come from nurseries. In contrast, the detection of M. incognita in nurseries alone suggests that this species could not reproduce in orchards because of either the competition with other plant-parasitic nematodes or unfit local habitats. The impact of environmental variables (climate, habitat origin and physicochemical characteristics of the substrates) on the distribution of Meloidogyne species is also discussed.
Conclusion
Olive nurseries in Morocco are not able to guarantee the safety of rooted plants. As a result, olive production systems are exposed to strong RKN invasion risks. Consequently, the use of healthy substrates in nurseries may prevent plant-parasitic nematode induction in orchards.
Growth and ontogeny of digestive function were studied in pikeperch (Sander lucioperca) larvae weaned on artificial food at different ages. Three weaning treatments initiated respectively on day 9 (W9), day 15
(W15) or day 21 (W21) post-hatching (p.h.) were compared with a control group, fed Artemia nauplii from first feeding until the end of the rearing trial on day 36 p.h. The digestive enzyme activities and the ontogeny
of digestive structures were investigated using enzymatic assays and histological methods. Growth of pikeperch larvae was
significantly affected by precocious weaning. Pancreatic (trypsin and amylase) and intestinal (leucine-alanine peptidase,
leucine aminopeptidase N and alkaline phosphatase) enzyme activities were detected from hatching onwards, increased at the
moment of first feeding and then decreased. Pepsin secretion occurred at day 29 p. h. only, concurrently with the stomach
development and differentiation of gastric glands. In the early weaning group (W9) the maturation process of intestinal enterocytes
seems to be impaired and/or delayed and several signs of malnutrition were recorded. Except for alkaline phosphatase activity,
no differences in enzyme activities and development of digestive structures were observed among the control, W21, and W15
groups. Moreover, at the end of the experiment, no differences in proteolytic activities were observed among larvae from the
different treatments, indicating that, in surviving individuals, the digestive structures were properly developed and the
larvae had acquired an adult mode of digestion. Based on the artificial diet used, our results suggested that pikeperch larvae
can be weaned from day 15 p.h. without significant adverse effect on digestive capacities (except for alkaline phosphatase)
or development of digestive tract, while earlier weaning impaired the onset of the maturation processes of the digestive system,
both in terms of morphological structures and enzymatic activities. 相似文献
Soil compaction is one of the major problems facing modern agriculture. Overuse of machinery, intensive cropping, short crop rotations, intensive grazing and inappropriate soil management leads to compaction. Soil compaction occurs in a wide range of soils and climates. It is exacerbated by low soil organic matter content and use of tillage or grazing at high soil moisture content. Soil compaction increases soil strength and decreases soil physical fertility through decreasing storage and supply of water and nutrients, which leads to additional fertiliser requirement and increasing production cost. A detrimental sequence then occurs of reduced plant growth leading to lower inputs of fresh organic matter to the soil, reduced nutrient recycling and mineralisation, reduced activities of micro-organisms, and increased wear and tear on cultivation machinery. This paper reviews the work related to soil compaction, concentrating on research that has been published in the last 15 years. We discuss the nature and causes of soil compaction and the possible solutions suggested in the literature. Several approaches have been suggested to address the soil compaction problem, which should be applied according to the soil, environment and farming system.
The following practical techniques have emerged on how to avoid, delay or prevent soil compaction: (a) reducing pressure on soil either by decreasing axle load and/or increasing the contact area of wheels with the soil; (b) working soil and allowing grazing at optimal soil moisture; (c) reducing the number of passes by farm machinery and the intensity and frequency of grazing; (d) confining traffic to certain areas of the field (controlled traffic); (e) increasing soil organic matter through retention of crop and pasture residues; (f) removing soil compaction by deep ripping in the presence of an aggregating agent; (g) crop rotations that include plants with deep, strong taproots; (h) maintenance of an appropriate base saturation ratio and complete nutrition to meet crop requirements to help the soil/crop system to resist harmful external stresses. 相似文献
Allergic diseases occur in most mammals, although some species such as humans, dogs and horses seem to be more prone to develop allergies than others. In horses, insect bite hypersensitivity (IBH), an allergic dermatitis caused by bites of midges, and recurrent airway obstruction (RAO), a hyperreactivity to stable born dust and allergens, are the two most prevalent allergic diseases. Allergic diseases involve the interaction of three major factors: (i) genetic constitution, (ii) exposure to allergens, and (iii) a dysregulation of the immune response determined by (i) and (ii). However, other environmental factors such as infectious diseases, contact with endotoxin and degree of infestation with endoparasites have been shown to influence the prevalence of allergic diseases in humans. How these factors may impact upon allergic disease in the horse is unknown at this time. The 3rd workshop on Allergic Diseases of the Horse, with major sponsorship from the Havemeyer Foundation, was held in Hólar, Iceland, in June 2007 and focussed on immunological and genetic aspects of IBH and RAO. This particular venue was chosen because of the prevalence of IBH in exported Icelandic horses. The incidence of IBH is significantly different between Icelandic horses born in Europe or North America and those born in Iceland and exported as adults. Although the genetic factors and allergens are the same, exported adult horses show a greater incidence of IBH. This suggests that environmental or epigenetic factors may contribute to this response. This report summarizes the present state of knowledge and summarizes important issues discussed at the workshop. 相似文献
Protein isolate from green gram (Phaseolus aureus) was prepared and the chemical composition was determined. It contained 64.04% protein, 1.8% total lipids, 27.64% total carbohydrates, 1.68% crude fibre and 4.84% ash. Iron, calcium, magnesium, copper, zinc, potassium and sodium were determined. The limiting amino acid in the protein isolate was lysine. In vitro digestibility pepsin followed the pancretion was the highest and the lowest was the digestion by pepsin alone. Water absorption, oil absorption, emulsion capacity and nitrogen solubility index (NSI) of the protein isolate were 2.26g/g, 1.24g/g, 31.4g/g and 6.8g/g, respectively. For comparison the same functional properties were determined for the flour of green gram. Replacing 5 and 10% of the wheat flour with green gram flour improved the mixing properties of dough and produced good acceptable bread. However, the addition of 15% green gram flour weakened the dough and lowered the quality of bread. Replacing 2.5, 5 and 7.5% of wheat flour with protein concentrate also weakened the mixing properties of the wheat dough and decreased the bread quality. 相似文献
Antibacterial activity of essential oil of dried inflorescence of Cymbopogon nervatus was investigated. The essential oil remarkably inhibited the growth of tested bacteria except for Salmonella typhi. The maximum activity was against Shigella dysenteriae and Klebsiella pneumoniae. 相似文献
Intraperitoneal inoculation of rats with Trypanosoma congolense (Federe strain) produced a sustained parasitaemia from days 7 to 23 post-infection (pi). The fasting tail-blood glucose (FBG) concentrations in the infected animals increased (p<0.05) from 3.8+/-0.2 mmol/l on day 0 pi to 4.6+/-0.2, 4.9+/-0.2 and 5.8+/-0.3 mmol/l on days 7, 10 and 17 pi and decreased (p<0.05) to 3.1+/-0.8 and 2.9+/-0.7 mmol/l on days 20 and 23 pi, but the values in the uninfected controls varied between 3.8+/-0.3 mmol/l on day 0 pi and 3.9+/-0.2 mmol/l on day 23 pi. After oral glucose intake (1.0 g/kg) and determination of tail-blood glucose (BG) concentrations after 2 h, the percentage increase in BG from FBG was either comparable in infected and uninfected groups (days 7, 20, 23 pi) or lower (p<0.05) in the infected group (days 10, 17), suggesting the same rate of tissue glucose delivery in both groups or a faster rate in the infected group. Therefore, oral glucose tolerance in the infected rat was not impaired, but there was initial fasting hyperglycaemia followed by fasting hypoglycaemia in the later stage. 相似文献
Au cours du printemps 2002, une grave maladie s'est manifestée dans une culture de tomate (cv. Collibri) de primeur sous abris-serres dans une exploitation située à Chott Mariem (120 km au sud de Tunis). Les plantes attaquées montrent les symptômes caractéristiques d'une maladie vasculaire. L'isolement de l'agent pathogène à partir des vaisseaux à différents niveaux de la tige des plantes malades a révélé systématiquement la présence de Verticillium alboatrum . La virulence de ce nouveau pathotype de V. alboatrum a été vérifiée sur quatre cultivars de tomate portant le gène de résistance Ve et comparée à un témoin sensible. Ce nouveau pathotype a montré une virulence accrue aussi bien chez les cultivars résistants que chez le témoin sensible entraînant une réduction de la croissance de 18%à 34%, le dessèchement des feuilles et le brunissement des vaisseaux. Ces résultats confirment la présence pour la première fois en Tunisie d'un nouveau pathotype de V. alboatrum pouvant attaquer les cultivars de tomate pourvus du gène de résistance Ve . 相似文献