Application of a low-cost camera on a UAV to estimate maize nitrogen-related variables

Precision Agriculture - The development of small unmanned aerial vehicles and advances in sensor technology have made consumer digital cameras suitable for the remote sensing of vegetation. In this...     

Effects of defoliation on whole‐plant maize characteristics as forage and energy crop

Hail affects yield and quality of maize crops, and consequences also depend on the growth stage at which the injury occurred. Whole‐plant maize (WPM) silage is often used within the same farm for cattle feeding and biogas production. The present study aimed to verify the effects of hail damage, simulated by artificial defoliation, on yield and chemical and nutritional features, as well as on biochemical methane potential (BMP) of maize forage. In a randomized block design with three replicates, four defoliation levels (0%, 33%, 66% and 100% of leaf area removal respectively) have been applied at either the V12 (12th leaf), R1 (silking) or R3 (milk) stages for two consecutive years. WPM yield, chemical and nutritional features, and BMP were measured. Dry‐matter (DM) yield per hectare was progressively reduced (p < 0.001) with increasing levels of defoliation and with application at V12 in comparison with R1 or R3 (1.26 vs. 1.39 and 1.46 kg ha^?1 for V12 vs. R1 and R3; p < 0.003). Nutritive value and BMP per unit of product were less altered than dry‐matter yield per hectare by defoliation. Anticipating defoliation reduced net energy for lactation (5.26 vs. 5.46 MJ kg^?1 DM for V12 and R3 respectively; p = 0.02). Total defoliation resulted in an accumulation of nitrates (NO₃) compared to the other treatments (3.98 vs. 1.53 g NO₃ kg^?1 DM; p < 0.001). BMP was mainly reduced by early and complete defoliation. Equations were developed to estimate the effects of defoliation on yield, composition, and nutritive and energetic values of WPM.     

Ecotoxicological evaluation of Harbour sediments using marine organisms from different trophic levels

Background, Aim and Scope  The toxicity of contaminated sediments should be evaluated considering the direct exposure of laboratory organisms to whole sediments and the indirect exposure to elutriates or extracts (Tay et al. 1992, Byrne and Halloran 1999, Nendza 2002). The alga Dunaliella tertiolecta is indicated for the use in toxicity bioassays because it is highly sensitive to several xenobiotics. Harpacticoid copepods have been already used for toxicity testing and Tigriopus fulvus is a promising Mediterranean target-species in ecotoxicology (Todaro et al. 2001, Faraponova et al. 2003, Pane et al. 2005a). In this study, the toxicity of sediments collected in harbour sites of the Northeastern Adriatic Sea was evaluated by growth inhibition test with free living and alginate-immobilized Dunaliella tertiolecta and acute toxicity test with nauplii and adult Tigriopus fulvus with the aim of pointing out the importance to utilize model organisms from different trophic levels in sediment ecotoxicology. Methodology  Elutriates and whole sediments were tested on free living and immobilized (Pane et al. 1998) algal cells, and on laboratory reared copepods. Free-living D. tertiolecta were exposed to diluted elutriates in a static, multi-well plate system. Naalginate immobilized D. tertiolecta were placed in polystyrene inserts fitted with polyester mesh bottoms and exposed to a thin layer (2 mm) of whole sediments in multi-well plates (EPS 1992, Pane and Bertino 1999). Toxicity tests with copepods were carried out on Tigriopus fulvus nauplii (elutriates) and adults (whole sediments and elutriates). Same-aged nauplii useful for toxicity tests were obtained by egg sac detaching and consequent hatching stimulation (Pane et al. 2006). Newborn nauplii (I–II stage) were exposed to elutriates in multi-well plates provided with polystyrene inserts. Adult T. fulvus maintained in polystyrene inserts fitted with polyester mesh bottoms were placed in contact with a thin layer (2 mm) of whole sediment placed on multi-well plate bottoms. All end-points were evaluated after 96 h. Results  In general, the effects increased with the increasing of elutriate concentration up to 50%; the stimulation or inhibition of algal growth was statistically significant in comparison to the control. The inhibiting elutriates induced EC₅₀ variations of algal growth ranging from 66.9% to 74.3%. The mortality of T. fulvus nauplii was always < 25% after treatment with 100% elutriates and < 10% after treatment with 50% dilution; no effect was shown up with 25% dilution; therefore LC₅₀ was not calculable. The effect of elutriates was negligible on adult copepods and LC₅₀ values were never calculable; percent mortality always resulted in < 10% after treatment with whole sediments. Discussion  Both experimental systems gave substantially similar results after exposition to whole sediments and elutriates. During the experiment with algal cells, the immobilization in Na-alginate and the employment of inserts which allowed the contact of organisms with sediments and their easy counting were particularly useful. Likewise, the employment of inserts of adequate mesh size in the tests with copepods allowed the contact of organisms with the sediment and made organism handling and counting easy, as well as the evaluation of mortality. The methodology here described and the utilization of the proposed test-species could have an importance also considering that the current trend in ecotoxicological research is towards finding the most appropriate organism for specific areas of concern by using indigenous species (Mariani et al. 2006) and towards the major significance of chronic and reproductive end-points. Conclusions  Based on the above results, it can be stated that the bioassay with Dunaliella tertiolecta could be a good estimation tool for the ecotoxicological assessment of marine sediments. The immobilization of algae in Na-alginate was seen to be useful to evaluate the toxicity of whole sediments; the employment of polystyrene inserts allowed an improvement of the procedures. T. fulvus nauplii and adults, as other harpacticoids such as Tigriopus japonicus (Yoon et al. 2006), satisfy the basic criteria for the employment of a standard species in marine bioassays. To date only pelagic Acartia tonsa are utilized in the standardized procedure to evaluate the risk assessment of chemicals or wastewaters (ISO 1999). As, on the contrary, the exposure of copepods to solid-phase contaminants it is not yet standardized, the employment of polystyrene inserts improved the procedures for T. fulvus too. So, the rapidity and the possibility to solve practical problems could be the main attractive features of this technique (Pane et al. 2005a) when applied to whole sediments. Recommendations and Perspectives  The methodology here developed being also applicable to long term and reproduction tests should be recommended because it provides relevant information in comparison with other frequently applied, standardized biotests with crustaceans (ISO 1999). The procedure has been shown to be easily applicable to selected marine organisms. ESS-Submission Editor: Prof. Dr. Henner Hollert (henner.hollert@bio5.rwth-aachen.de)     

Linkage disequilibrium and effective population size in Gir cattle selected for yearling weight

Linkage disequilibrium (LD) plays an important role in genomic selection and mapping of quantitative trait loci (QTL). This study investigated the pattern of LD and effective population size (N_e) in Gir cattle selected for yearling weight. For this purpose, 173 animals with imputed genotypes (from 18 animals genotyped with the Illumina BovineHD BeadChip and 155 animals genotyped with the Bovine LDv4 panel) were analysed. The LD was evaluated at distances of 25–50 kb, 50–100 kb, 100–500 kb and 0.5–1 Mb. The N_e was estimated based on 5 past generations. The r² values (a measure of LD) were, respectively, .35, .29, .18 and .032 for the distances evaluated. The LD estimates decreased with increasing distance of SNP pairs and LD persisted up to a distance of 100 kb (r² = .29). The N_e was greater in generations 4 and 5 (24 and 30 animals, respectively) and declined drastically after the last generation (12 animals). The results showed high levels of LD and low N_e, which were probably due to the loss of genetic variability as a consequence of the structure of the Gir population studied.     

2n gametes inSolanum tuberosum dihaploids

Pollen stainability over two years and microsporogenesis were investigated in seven dihaploids extracted fromSolanum tuberosum tetraploids (AVRDC-1287.19, Conchita, Merrimack and W231). Two dihaploids proved to be male-sterile and male gamete abortion is likely to be post-meiotic because a regular meiosis occurred. The other dihaploids proved to be partially male-fertile and 2n pollen producers, as well. Almost all clones showed predominantly the formation of parallel spindles. Correlations estimated between the observed abnormalities in spindle orientation and the meiotic products evidenced a high correlation between parallel/fused spindles and dyads. The dihaploids were also used as parents in crosses with tetraploids. One berry with 44 seeds was obtained from dihaploid AVI 24 used as pollen parent in 4x × 2x crosses. After 2x × 4x crosses, three dihaploids including the two male-sterile were found to be 2n egg producers. The formation of 2n gametes inS. tuberosum dihaploids is discussed in relation to a direct use of dihaploids in sexual polyploidization schemes to combine useful traits in a superior genotype at 4x level.     

Mortality outbreak by perch rhabdovirus in European perch (Perca fluviatilis) farmed in Italy: Clinical presentation and phylogenetic analysis

This work reports a mortality outbreak, occurred in 2015 and affecting juveniles of European perch (Perca fluviatilis L.) farmed in Italy. Perch rhabdovirus (PRV) was detected by viral isolation and biomolecular investigations. Phylogenetic analysis clustered our isolate into genogroup B, which also includes PRV isolates from Perca fluviatilis identified in France (2004–2009); diagnostic investigations also revealed opportunistic bacteria (Aeromonas hydrophila) and parasites (Chilodonella piscicola). Since, occasionally, PRV has been reported in the natural environment, which is often a source of eggs and broodstock for farms, it could be possible that both similar France and Italian isolate were imported from a same place elsewhere and have a common origin. Improving biosecurity measures (batch control) and disinfection of egg strings with an iodine‐based solution helps prevent apparent vertical transmission of PRV.     

Assessment of the Antimicrobial Activity of Algae Extracts on Bacteria Responsible of External Otitis

External otitis is a diffuse inflammation around the external auditory canal and auricle, which is often occurred by microbial infection. This disease is generally treated using antibiotics, but the frequent occurrence of antibiotic resistance requires the development of new antibiotic agents. In this context, unexplored bioactive natural candidates could be a chance for the production of targeted drugs provided with antimicrobial activity. In this paper, microbial pathogens were isolated from patients with external otitis using ear swabs for over one year, and the antimicrobial activity of the two methanol extracts from selected marine (Dunaliella salina) and freshwater (Pseudokirchneriella subcapitata) microalgae was tested on the isolated pathogens. Totally, 114 bacterial and 11 fungal strains were isolated, of which Staphylococcus spp. (28.8%) and Pseudomonas aeruginosa (P. aeruginosa) (24.8%) were the major pathogens. Only three Staphylococcus aureus (S. aureus) strains and 11 coagulase-negative Staphylococci showed resistance to methicillin. The two algal extracts showed interesting antimicrobial properties, which mostly inhibited the growth of isolated S. aureus, P. aeruginosa, Escherichia coli, and Klebsiella spp. with MICs range of 1.4 × 10⁹ to 2.2 × 10¹⁰ cells/mL. These results suggest that the two algae have potential as resources for the development of antimicrobial agents.     

Residues of a Triazole Fungicide in Soil After 4 Years of Application to Sugar Beet

An experimental study to investigate the potential soil accumulation of the triazole fungicide difenoconazole in soil was carried out in northwestern Italy. The fungicide was applied to sugar beet for 4 years with three applications per year at a rate of 75 g ha^?1 each, according to formulated product recommended use. Soil cores were collected each year before the first application, after each application and at harvest of the crop. The soil samples were then split into 0–10 and 10–40 cm depth layers, extracted and quantitatively analysed by gas chromatography for difenoconazole residues. The study evidenced that difenoconazole residues could be detected in the upper soil layer only, in quantities detectable after several applications (0.14 to 0.32 mg kg^?1 after the third application) which then become undetectable the following year. It can be concluded, therefore, that difenoconazole does not accumulate in soil.     

Soil chemical and biochemical properties of a salt-marsh alluvial Spanish area after long-term reclamation

Marisma, one of the largest salt-marsh alluvial areas in SW Spain, has been reclaimed since 1970 by artificial drainage and amendment with phosphogypsum (PG) so as to reduce Na⁺ saturation. Within the reclaimed area, two 250- × 20-m plots were treated as follows: (1) amendment with 25 Mg/ha of PG every 2 to 3 years between 1979 and 2003 (plot PY); (2) like PY but PG treatment stopped after 1997 (plot DR). A contiguous virgin Marisma salt-marsh plot (MV), neither drained nor amended, was the control. In MV, soil microbial biomass C, most enzyme activities and total organic C content were much greater than in PY and DR soils, despite the salinity stress. The decrease in soil organic matter content in PY and DR soils was likely due to cotton-cropping practices, which favoured the organic C mineralisation and nutrients removal by crops. Microbial activity of MV soil, probably stimulated by the rhizodepositions of the natural vegetation, did not suffer from the osmotic effect due to the raising of soil solution ionic strength. Microbial quotient could be ranked as MV > PY > DR, whereas the metabolic quotient had an opposite trend. Thus, both quotients suggested that the interruption of PG amendment was not favouring microbial activity. Principal component analysis clearly identified the chemical and biochemical soil properties mostly affected by the reclamation and also indicated the longer PG amendment in PY plot. Stepwise discriminant analysis identified two physiologically different types of soil microflora, one less active present in the MV virgin soil and another more active present in the reclaimed PY and DR soils.