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1.
In Cameroon, andosols are suspected to be suppressive to cocoyam (Xanthosoma sagittifolium) root rot disease (CRRD) caused by the Oomycete pathogen Pythium myriotylum. To determine factors involved in disease suppressiveness, andosols were studied in comparison to ferralsols known to be disease-conducive. Soil samples were collected from six sites of which three were in andosols around Mount Cameroon (Boteva, Njonji, and Ekona) and the three others in ferralsols (Bakoa, Lapkwang, and Nko’o canane). Greenhouse plant experiments were used to assess soil suppressiveness. Soils were artificially infested with two levels of P. myriotylum inoculum (100 and 300 mycelia strands g−1 soil) prior to planting cocoyam. Disease severity was significantly higher in ferralsols than in andosols. Andosols partly lost their suppressiveness as a result of autoclaving and could recover suppressiveness following recolonisation by their original microflora. Soil microbial groups implicated in the disease suppression were investigated by assessing the effect of fungicide, bactericide, and pasteurisation on andosol suppressiveness. Andosols suppressiveness was significantly reduced following pasteurisation and treatment with fungicide and bactericide. The possible influence of microbial biomass on andosol suppressiveness was investigated by comparing microbial populations of suppressive andosols to those in andosols that had lost suppressiveness. A comparative analysis of suppressive and conducive soil properties was performed to identify soil variables, which may contribute to soil suppressiveness. Soil chemical analysis results showed that organic matter content was higher in andosols than in ferralsols. In addition, the content of mineral nutrients such as Ca, K, Mg and N, was higher in andosols than in ferralsols. These soil variables negatively correlated with disease severity. By contrast, sand and clay, which were higher in ferralsols than in andosols, were positively related to disease severity. This study has confirmed the suppressive nature of andosols from Mount Cameroon to CRRD. The results suggest that high organic matter content is likely mediating P. myriotylum suppression in andosols by improving soil structure, increasing soil nutrient content and microbial biomass, and sustaining microbial activity. 相似文献
2.
Fidèle Tiendrébéogo V.S. Edgar Traoré Jean-Michel Lett Nicolas Barro Gnissa Konaté Alfred S. Traoré Oumar Traoré 《Crop Protection》2010
The impact of okra leaf curl disease on four accessions of a local okra cultivar and four commercial okra cultivars was assessed in field conditions from June to October in 2007 and 2008. Disease incidence varied from 68.5% to 72.5% among accessions of the local cultivar while commercial cultivars were much less infected (8.7–16.2%). Diseased plants of the local cultivar suffered more reduced growth (58% reduction) than those of the commercial cultivars (39.6%). The number of marketable fruits per plant, the fruit length, fruit diameter and fruit weight which were subject to reductions of 26–61%, 19–64%, 6–42% and 23–63%, respectively. The overall yield losses were significantly higher in accessions of the local cultivar (26–55%) than in the commercial ones (4.4–9.6%). The average economic losses for one hectare of crop were estimated at of 11,100 USD and 1950 USD, respectively for the local and the commercial cultivars. 相似文献
3.
针对Inconel 718合金材料加工中不断提高的表面质量需求,研究了采用磁性复合流体(Magneticcompound fluid)抛光Inconel718合金材料的加工工艺.根据磁性复合流体抛光原理搭建Inconel718合金抛光实验平台,进行不同抛光方向、抛光时间、抛光转速等工艺参数下的Inconel718合金抛... 相似文献
4.
Oumar Ibrahima Farhat Chibani Sawsen A. Oran Mohamed Boussaid Yannis Karamanos Aly Raies 《Genetic Resources and Crop Evolution》2005,52(8):1087-1097
Allozyme variation was assessed in a collection of pearl millet cultivars derived from three different regions of traditional
cultivation of this cereal in Tunisia and West African countries. Using starch gel electrophoresis, 11 loci corresponding
to seven enzyme staining systems were identified. Important within-cultivar genetic diversity was detected. Genetic diversity
within Tunisian cultivars was similar and was more pronounced than for West African ones. This result could be explained by
the low level of the human selection characterizing the Tunisian cultivars. Most of the total genetic diversity is maintained
within subregions suggesting little genetic differentiation. Cluster analysis did not reveal separate clusters for the various
subregion cultivars. However the cluster analysis should help in the selection of interesting genotypes for future breeding
programs. 相似文献
5.
Studying soil nematofauna provides useful information on soil status and functioning but requires high taxonomic expertise. Near infrared reflectance (NIR) spectroscopy (NIRS) has been reported to allow fast and inexpensive determination of numerous soil attributes. Thus the present study aimed at assessing the potential of NIRS for determining the abundance and diversity of soil nematodes in a set of 103 clayey topsoil samples collected in 2005 and 2006 from agricultural soils in the highlands of Madagascar.The morphological characterization of soil nematofauna involved extraction through elutriation then counting under binoculars and identification at family or genus level using microscopy, on ca. 150-g fresh soil samples. Taxa were assigned to five trophic groups, namely bacterial feeders, fungal feeders, obligate plant feeders, facultative plant feeders, and omnivores and predators (together). In addition, four ecological indexes were calculated: the Enrichment index, Structure index, Maturity index, and Plant parasitic index.Oven-dried (40 °C) < 2-mm sieved 5-g soil subsamples were scanned in the NIR range (1100-2500 nm), then spectra were fitted to nematofauna data using partial least square regression. Depending on the sample set considered (year 2005, year 2006, or both years), NIRS prediction of total nematode abundance was accurate (ratio of standard deviation to standard error of cross validation, i.e. RPD ≥ 2) or acceptable (RPD ≥ 1.6). Predictions were accurate, acceptable, or quasi-acceptable (RPD ≥ 1.4) for several of the six most abundant taxa, and to a larger extent, for most trophic groups (except facultative plant feeders); but they could not be made for taxa present in a small number of samples or at low abundance. By contrast, NIRS prediction of relative abundances (in proportion of total abundance) was poor in general, as was also the prediction of ecological indexes (except for the 2006 set). On the whole, these results were less accurate than NIRS predictions of soil attributes often reported in the literature. However, though not very accurate, NIRS predictions were worthwhile considering the labor-intensity of the morphological characterization. Most of all, NIRS analyses were carried out on subsamples that were probably too small (5 g) to allow representative sampling of nematofauna. Using larger samples for NIRS (e.g. 100 g) would likely result in more accurate predictions, and is therefore recommended. Scanning un-dried samples could also help improve prediction accuracy, as morphological characterization was carried out on samples not dried after sampling.Examining wavelengths that contributed most to NIRS predictions, and chemical groups they have been assigned to, suggested that NIRS predictions regarding nematofauna depended on constituents of both nematodes and preys’ food. Predictions were thus based on both nematofauna and soil organic properties reflected by nematofauna. 相似文献
6.
Zon Aboubacar Oumar Kouassi Edouard Konan Ouédraogo Amadé 《Genetic Resources and Crop Evolution》2021,68(5):1731-1745
Genetic Resources and Crop Evolution - Palms constitute vital species for local people’s well-being, especially in West Africa. This analytic review aims at providing an overview of West... 相似文献
7.
Fotso Oumar Nicolas N Néhémie DT Denis ON 《Pakistan journal of biological sciences: PJBS》2008,11(5):726-732
A productive genotype of Irvingia gabonensis were cultured in vitro for induction embryogenic calli, somatic embryogenesis and regeneration of plantlets. Fragments of young leaves were used as primary explants. Callogenesis was initiated by culture of explants during 30 days on Murashige and Skoog medium half strength (MS/2) supplemented with 1-6 mg L(-1) of 2,4-dichlorophenoxyacetic acid (2,4-D). The highest percentage of explants forming calli is 85.1% at 3 mg L(-1) of 2,4-D. Somatic embryos were obtained after a subculture of embryogenic calli during 60 days on MS/2 supplemented with 1-3 mg L(-1) of BAP. The highest percentage of embryogenic calli which differentiates somatic embryos is 63.8 +/- 2.3% at 1 mg L(-1) of 6-benzylaminopurine (BAP). The highest number of somatic embryos per callus which is 43.6 is obtained with 2 mg L(-1) of this phytohormone. When isolated from calli and sub-cultured during 30 days on MS/2 supplemented with 2 mg L(-1) of BAP, somatic embryos germinate with a highest percentage of 83%. The subculture of germinated somatic embryos on the same Basal Medium (BM) supplemented with 4 mg L(-1) of BAP and 2 mg L(-1) of Naphthalene Acetic Acid (NAA) during 80 days gives rise to the plantlets with 82.7 +/- 4.8% of success. With this combination, each plantlet has average length of 5.6 cm, bears 3.3 leaves and 7.2 roots with 1 or 2 pivoting roots. Plantlets acclimatized on a mixture sterilized soil/vermiculite at equal volume survive at 93%. Results of this study constitute a new way for a production of Irvingia gabonensis seedlings with pivoting root and they permit to arrest the difficulties of natural and horticultural reproduction. 相似文献
8.
We carried out a stratified, cluster-randomised, controlled trial in south Mali in 2004 to evaluate the impact of providing information on the diagnosis and treatment of bovine trypanosomosis by farmers. We recruited cattle farmers (444) in 46 villages and used stratified, restricted-randomisation to assign villages to either the test or control group. Farmers in the test group received an information leaflet designed to address gaps in farmer knowledge likely to lead to inadequate treatment; their knowledge was assessed before the intervention, and at 2 weeks and 5 months after the intervention. We assessed the quality of farmer treatments by measuring clinical outcomes in cattle 2 weeks after selection and treatment. As an indicator of herd health, we assessed the mean hematocrit of the village herd before, and 5 months after, the intervention. To account for clustering, we analysed data using generalised estimating equations. Improvements in farmer knowledge of trypanosomosis diagnosis and treatment at 2 weeks and 5 months in the group receiving information were 23% and 14% greater at 2 weeks and 5 months, respectively. In the test group, 84% of farmer treatments were successful, compared to 73% in the control group. Giving rational drug-use information to farmers improved their knowledge and management of trypanosomosis as well as clinical outcomes in cattle they treated and had no discernible negative impacts. 相似文献
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10.
Missohou A Mbodj M Zanga D Niang S Sylla KS Seydi M Cissé O Seck SW 《Tropical animal health and production》2011,43(5):983-988
A total of 100 samples of poultry meat were collected in poultry farms in the vicinity of the Mbeubeuss landfill in the Niayes (Senegal) for microbiological and chemical analysis. Fifty-four (54) samples were collected in farms located less than 1 km from the landfill and 46 samples were collected in farms located a bit further (more than 1 km from the landfill). Microbiological quality was determined using techniques recommended by Association Française de Normalisation (AFNOR). Lead and cadmium concentration in poultry meat was measured by flame spectrometry while total mercury was determined by atomic absorption spectrometry. Three percent (3%) of the samples’ quality were unsatisfactory for E. coli, 1% for Staphylococci and 7% for Salmonella spp. Poor meat quality was found either in farms located less than 1 km of the landfill or in farms located at more than 1 km of the landfill. Except for Salmonella, only meat samples from poultry receiving drinking water from well showed unsatisfactory microbiological quality. The samples were free of cadmium and lead but were contaminated by mercury. Sixty-eight percent (68%) of the samples contained mercury with a high contamination level (>0.011 mg/kg) in 20% of the samples. No significant difference was found between the farms that were nearest to and further away from the landfill while the source of drinking water seemed to be the main cause of contamination of poultry meat by mercury. 相似文献