Strengthening understanding and perceptions of mineral fertilizer use among smallholder farmers: evidence from collective trials in western Kenya     

Michael Misiko  Pablo Tittonell  Ken E. Giller  Paul Richards 《Agriculture and Human Values》2011,28(1):27-38

It is widely recognized that mineral fertilizers must play an important part in improving agricultural productivity in western Kenyan farming systems. This paper suggests that for this goal to be realized, farmers’ knowledge must be strengthened to improve their understanding of fertilizers and their use. We analyzed smallholder knowledge of fertilizers and nutrient management, and draw practical lessons from empirical collective fertilizer-response experiments. Data were gathered from the collective fertilizer-response trials, through focus group discussions, by participant observation, and via in-depth interviews representing 40 households. The collective trials showed that the application of nitrogen (N) or phosphorous (P) alone was insufficient to enhance yields in the study area. The response to P on the trial plots was mainly influenced by incidences of the parasitic Striga weed, by spatial variability or gradients in soil fertility of the experimental plots, and by interactions with N levels. These results inspired farmer to design and conduct experiments to compare crop performance with and without fertilizer, and between types of fertilizers, or responses on different soils. Participating farmers were able to differentiate types of fertilizer, and understood rates of application and the roles of respective fertilizers in nutrient supply. However, notions were broadly generated by unsteady yield responses when fertilizers were used across different fertility gradients, association with high cost (especially if recommended rates were to be applied), association of fertilizer use with hybrids and certain crops, historical factors, among other main aspects. We identified that strengthening fertilizer knowledge must be tailored within existing, albeit imperfect, systems of crop and animal husbandry. Farmers’ perceptions cannot be changed by promoting more fertilizer use alone, but may require a more basic approach that, for example, encourages farmer experimentation and practices to enhance soil properties such as carbon build-up in impoverished local soils.  相似文献   

Genetic mapping,marker assisted selection and allelic relationships for the Pu6 gene conferring rust resistance in sunflower     

Mariano Bulos  Pablo Nicolas Vergani  Emiliano Altieri 《Breeding Science》2014,64(3):206-212

Rust resistance in the sunflower line P386 is controlled by Pu₆, a gene which was reported to segregate independently from other rust resistant genes, such as R₄. The objectives of this work were to map Pu₆, to provide and validate molecular tools for its identification, and to determine the linkage relationship of Pu₆ and R₄. Genetic mapping of Pu₆ with six markers covered 24.8 cM of genetic distance on the lower end of linkage Group 13 of the sunflower consensus map. The marker most closely linked to Pu₆ was ORS316 at 2.5 cM in the distal position. ORS316 presented five alleles when was assayed with a representative set of resistant and susceptible lines. Allelism test between Pu₆ and R₄ indicated that both genes are linked at a genetic distance of 6.25 cM. This is the first confirmation based on an allelism test that at least two members of the R_adv/R₄/R₁₁/ R_13a/R_13b/Pu₆ cluster of genes are at different loci. A fine elucidation of the architecture of this complex locus will allow designing and constructing completely new genomic regions combining genes from different resistant sources and the elimination of the linkage drag around each resistant gene.  相似文献   

Mass trapping is as effective as ground bait sprays for the control of Anastrepha (Diptera: Tephritidae) fruit flies in mango orchards          下载免费PDF全文

Jorge Villalobos  Salvador Flores  Pablo Liedo  Edi A Malo 《Pest management science》2017,73(10):2105-2110

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Foraging behavior of heifers with or without social models in an unfamiliar site containing high plant diversity     

Mauricio Velázquez-Martínez  Silvia López-Ortiz  Omar Hernández-Mendo  Pablo Díaz-Rivera  Sergio Pérez-Elizalde  Jaime Gallegos-Sánchez 《Livestock Science》2010,131(1):73-82

Grazing behavior, diet selection and weight gain of heifers (with or without social models) were assessed in an unfamiliar site containing high plant diversity. The study was performed within a tropical forest ecosystem containing a mixture of grass forb/herb, shrub and tree species. Ten inexperienced crossbred Bos taurus × Bos indicus heifers (7 ± 1 months old) were randomly assigned to one of two groups: naive or naive + social model (sm) and two experienced heifers (16 months old) were assigned to the second group. Naive heifers were bottle-nursed from days 2 to 90 after birth and began grazing at 1 month of age in tropical grass monocultures, while experienced animals had been foraging in sites containing a high diversity of plant species for 3 months prior to the study. Each group grazed in separate paddocks for a 12-week period during the rainy season, and animals were observed using focal sampling from 7:00 to 19:30 h to assess diet composition based on bite counts. Weight gain was assessed every 14 days. Paddocks contained from 1481 to 1789 kg/ha of herbaceous dry matter, enough to support the heifers throughout the study without affecting diet selection. Shrub and tree cover ranged from 55.2 to 58.4% across treatments. Bites per minute were adjusted to a log-scaled quadratic-plateau model and the curves showed no differences between treatments (P = 0.756). However, diet composition differed between groups (P < 0.001), with naive + sm heifers ingesting a greater proportion of trees (P < 0.001) and shrubs (P = 0.02), while naive heifers ingested more forb/herbs (P = 0.02); no difference in grass consumption was observed (P = 0.92). Heifers in both treatments consumed the same plant species (50 from 26 families). Over time, utilization of several plant species increased or decreased (P < 0.05), eventually leveling off for the remainder of the study. Although differences in diet composition were observed, they did not affect overall weight gain (117 and 113 g/day in the naive and naive + sm groups, respectively; P = 0.913). However, initial post-weaning weight loss was avoided in the naive + sm group. Social learning facilitates a higher use of shrubs and trees in tropical pastures containing a high diversity of plant species with different growth habits. As many plant species have high potential as forage, more effort should be placed on developing mechanisms to increase their dietary inclusion by cattle.  相似文献   

Evaluation of lufenuron as a chemosterilant against fruit flies of the genus Anastrepha (Diptera: Tephritidae)     

Pilar Moya  Salvador Flores  Ildefonso Ayala  Juan Sanchis  Pablo Montoya  Jaime Primo 《Pest management science》2010,66(6):657-663

BACKGROUND: Chemosterilisation with lufenuron bait stations is a recently developed technique that is being implemented for Ceratitis capitata Wiedemann control. The aim of this work was to evaluate the chemosterilising effect of lufenuron against four economically important Latin American fruit flies species: Anastrepha ludens (Loew.), A. obliqua Macquart, A. serpentina Wiedemann and A. striata Schiner (Diptera: Tephritidae) in order to design a similar strategy for their control. RESULTS: Sexually mature adults were treated by ingestion with concentrations ranging from 0.1 to 30.0 mg g^?1 of lufenuron in the diet. In addition, conspecific crosses with only one of the sexes being treated (30.0 mg g^?1) were performed in order to appraise the contribution of each sex to the sterilising effect. In all cases, fecundity was not affected by the treatments, as opposed to fertility where all Anastrepha species studied were significantly affected, although to different extents. The conspecific crosses showed that treated males of A. ludens, A. obliqua and A. serpentina were not able to transmit the sterility to their respective untreated females. Only in the case of A. striata did crossing treated males with untreated females significantly reduced egg hatch. CONCLUSION: Although further investigations are required, the present results demonstrate that the use of lufenuron for controlling A. striata could be potentially viable. Copyright © 2010 Society of Chemical Industry  相似文献   

Evaluation of an indirect oscillometric blood pressure monitor in normotensive and hypotensive anesthetized dogs     

Andre Shih DVM  DACVA  Sheilah Robertson BVMS  PhD  DACVA  DECVAA  Alessio Vigani MV  Anderson Da Cunha DVM  MS  Luisito Pablo DVM  MS  DACVA  Carsten Bandt DVM  DACVECC 《Journal of Veterinary Emergency and Critical Care》2010,20(3):313-318

Objective – To determine the accuracy and precision of an oscillometric noninvasive blood pressure device as a predictor of invasive direct blood pressure in healthy anesthetized hypotensive and normotensive dogs. Design – Prospective observational study. Setting – University teaching hospital. Animals – Eight crossbred adult dogs. Interventions – Anesthesia was induced with propofol and maintained with isoflurane. A catheter was placed in the dorsal pedal artery to record systolic, mean, and diastolic arterial blood pressures (aSAP, aMAP, and aDAP, respectively). The noninvasive blood pressure device cuff was placed around the contralateral front limb to record noninvasive systolic, mean, and diastolic blood pressure (nSAP, nMAP, and nDAP). Two states of blood pressure (BP) were studied: baseline state was established by keeping end‐tidal isoflurane concentration at 1.2±0.1%. The hypotensive state was achieved by maintaining the same isoflurane concentration while withdrawing approximately 40% of the animal's blood volume until aMAP was stable at approximately 40 mm Hg. At the end of the study, blood was returned to the animal and it was allowed to recover from anesthesia. Measurements and Main Results – Agreement between the direct and indirect BP measurements was determined by the Bland‐Altman method. The SAP and MAP but not DAP bias varied significantly between each BP state. Normotensive absolute biases (mean [SD]) for SAP, MAP, and DAP were ?14.7 mm Hg (15.5 mm Hg), ?16.4 mm Hg (12.1 mm Hg), and ?14.1 mm Hg (15.8 mm Hg), respectively. Absolute biases during the hypotensive state for SAP, MAP, and DAP were ?32 mm Hg (22.6 mm Hg), ?24.2 mm Hg (19.5 mm Hg), and ?16.8 mm Hg (17.2 mm Hg), respectively. Conclusion – The oscillometric device was not reliably predictive of intra‐arterial BP during hypotension associated with acute hemorrhage.  相似文献   

Could artificial reforestations provide as much production and diversity of fungal species as natural forest stands in marginal Mediterranean areas?     

Juan Andrés Oria-de-Rueda  María Hernández-Rodríguez  Pablo Martín-Pinto  Valentín Pando  Jaime Olaizola 《Forest Ecology and Management》2010

The aim of this work was to study and describe fungal communities in different habitats in dry Mediterranean areas. The objective was to determine whether artificial reforestations can develop fungal communities as productive and diverse as those found in natural stands. The results could provide ecological and economical implications for forest management in marginal areas, in order to recover the original forest dominated by Quercus, establishing as intermediate stage new forest stands dominated by Pinus which might play an essential role in restoring some type of degraded or marginal areas.  相似文献   

Root-lesion nematodes of the genus Pratylenchus (Nematoda: Pratylenchidae) from Costa Rica with molecular identification of P. gutierrezi and P. panamaensis topotypes     

Tatiana Zamora Araya  Walter Peraza Padilla  Antonio Archidona-Yuste  Carolina Cantalapiedra-Navarrete  Gracia Liébanas  Juan E. Palomares-Rius  Pablo Castillo 《European journal of plant pathology / European Foundation for Plant Pathology》2016,145(4):973-998

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The pyrethroid resistance status and mechanisms in Aedes aegypti from the Guerrero state,Mexico     

H. Angélica Aponte  R. Patricia Penilla  Felipe Dzul-Manzanilla  Azael Che-Mendoza  Alma D. López  Francisco Solis  Pablo Manrique-Saide  Hilary Ranson  Audrey Lenhart  Philip J. McCall  Américo D. Rodríguez 《Pesticide biochemistry and physiology》2013

Dengue is one of the most important vector-borne diseases worldwide and is a public health problem in Mexico. Most programs in dengue endemic countries rely on insecticides for Aedes control. In Mexico, pyrethroid insecticides (mainly permethrin and deltamethrin) have been extensively used over a decade as adulticides and represented a strong selection for insecticide resistance for dengue vectors in several parts of the country. We studied the type, frequency and distribution of insecticide resistance mechanisms in Aedes aegypti from six municipalities in the state of Guerrero selected on the basis of historically intense chemical control and a high risk for dengue transmission. Ae. aegypti eggs were collected from October 2009 to January 2010 using ovitraps. F₁ adults, emerged from these collections, were exposed to permethrin, deltamethrin and DDT in WHO diagnostic tests and showed high resistance levels to both pyrethroids and DDT. This was consistent with the presence of increased metabolic enzyme activities and target site insensitivity due to kdr mutations. Biochemical assays showed elevated esterase and glutathione S-transferase activities in the six municipalities. The V1016I kdr mutation on the IIS6 domain of the sodium channel gene was present in an overall frequency of 0.80. A second mutation, F1534C on the IIIS6 domain of the same gene was also detected, being the first report of this mutation in Guerrero. The multiple resistance mechanisms present in Ae. aegypti from Guerrero state represent a warning for the efficacy of the pyrethroid usage and consequently for the success of the dengue control program.  相似文献   

Evaluation of nonpolar metabolites in plant extracts by 13C NMR spectroscopy     

Palomino-Schätzlein M  Escrig PV  Boira H  Primo J  Pineda-Lucena A  Cabedo N 《Journal of agricultural and food chemistry》2011,59(21):11407-11416

(13)C nuclear magnetic resonance (NMR) spectroscopy was explored as a simple and efficient technique for the quantitative analysis of nonpolar metabolites in plants. The method was first optimized with a mixture of known metabolites and then applied to the nonpolar leaf extracts of plants harvested in the Valencian community (eastern Spain) belonging to three different genera: Euphorbia (Euphorbiaceae), Araujia (Apocynaceae), and Morus (Moraceae). Furthermore, an exhaustive analysis of Euphorbia characias leaf and stem extracts from different geographic locations allowed that quantitative (13)C NMR spectroscopy is a suitable tool for metabolic profiling purpose.  相似文献