Freshwater conservation in a fragmented world: Dealing with barriers in a systematic planning framework

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Availability of minerals in rendered meat and bone meal for Nile tilapia: Preliminary observations

A digestibility trial was conducted with 180 Nile tilapia (32.65 ± 4.52 g) fed a reference diet containing 350 g/kg crude protein and 4,500 kcal/kg gross energy. Five different meat and bone meals (MBMs) were evaluated. The test diets compound by 70% of reference diet and 30% of each MBM were elaborated and classified according to ash content: MBM‐430, MBM‐400, MBM‐370, MBM‐340 and MBM‐310. The apparent availability coefficient (AAC) of minerals and the apparent digestibility coefficient (ADC) of dry matter (DM) were subjected to one‐way analysis of variance (p < .05). Differences among ADC and AAC were determined by Tukey's multiple range test (p < .05). When appropriate, a polynomial regression analysis was performed. Linear correlation analyses between MBM chemical composition and the AAC and ADC were performed (p < .01). Higher values of ADC_DM, AAC_Ca and AAC_P were observed in MBM‐310, while low values were observed in MBM‐430. Quadratic effects of ash, P and Ca contents on AAC_Ca, AAC_P and ADC_DM were observed. The AAC_Ca, AAC_P and ADC_DM indicated a negative correlation with ash, P and Ca contents. MBM‐310 exhibited the highest mineral AAC, which could be used as a mineral source for Nile tilapia.     

Could the Supply of Boron and Zinc Improve Resistance of Potato to Early Blight?

The adequate supply of boron (B) and zinc (Zn) can improve the structural integrity and permeability of cell membranes, which is a defence mechanism against fungi infection. A greenhouse experiment was conducted to investigate the effect of the application of B and Zn on plant growth and the incidence and severity of potato early blight, a destructive foliar disease of potato crop caused by Alternaria grandis E.G. Simmons. Potato plants (Solanum tuberosum L. cv. Ágata) were grown in 11-l pots filled with sandy soil, unfertilized or fertilized with 5 mg kg^?1 B and 5 mg kg^?1 Zn (either alone or in combination). Potato plants were inoculated with isolates of Alternaria grandis at 40 days after planting. Early blight incidence and severity were evaluated visually 7 days after inoculation with A. grandis isolates. Disease incidence ranged from 16 to 41% infected leaves, and was significantly highest in the treatment with the application of B, followed by the control, and lowest with application of Zn and B + Zn. Early blight severity ranged from 2.5 to 25%, and was significantly higher in the unfertilized treatment than in those fertilized with Zn either alone or in combination with B. These findings suggest that Zn plays a critical role in potato tolerance to early blight and should be considered as a preventive measure in the disease management plan, since application of zinc reduced the incidence and severity of potato early blight. However, the physiological basis of this remains unknown.     

Characterization of field‐evolved resistance to Bacillus thuringiensis‐derived Cry1F δ‐endotoxin in Spodoptera frugiperda populations from Argentina

BACKGROUND

Transgenic maize (Zea mays L.) event TC1507 (Herculex^® I insect protection), expressing Cry1F δ‐endotoxin derived from Bacillus thuringiensis var. aizawai, was commercialized in 2003 in the Americas. Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) susceptibility to Cry1F was monitored annually across several regions in Argentina using diagnostic concentration bioassays. Reduced performance of TC1507 maize against S. frugiperda was reported in 2013. A resistant population was established in the laboratory and the dominance of Cry1F resistance was characterized.

RESULTS

During 2012–2015, high‐survivorship of several populations was observed in the resistance monitoring program. Reciprocal crosses of a Cry1F‐resistant population with a Cry1F‐susceptible population were evaluated to calculate effective dominance (D_ML) based on mortality levels observed at 100 µg/ml Cry1F. Two additional dominance levels (D_LC and D_EC) were calculated using lethal (LC₅₀) or effective concentration (EC₅₀) derived from concentration–response bioassays. Estimates indicated that Cry1F resistance in S. frugiperda in Argentina was either highly recessive (D_ML = 0.005) or incompletely recessive (D_LC < 0.26 and D_EC < 0.19).

CONCLUSION

This study is the first documented confirmation and characterization of S. frugiperda Cry1F field‐evolved resistance in Argentina. The resistance to Cry1F in S. frugiperda populations collected in Argentina, is autosomal and incompletely recessive similar to the resistance reported in Brazil. © 2017 The Authors. Pest Management Science published by John Wiley © Sons Ltd on behalf of Society of Chemical Industry.     

Sodium fluorescein as an internal tracer on the location of bovine urine patches in pastures

Sodium fluorescein (SF) was evaluated and validated as an internal marker in cattle for the location of urine patches in pastures. Three trials were carried out aiming at the following: evaluating the effect of dilution and volume of application on SF fluorescence on the environment; testing dosages and duration of excretion of SF administered orally to cattle; and validating the methodology for SF use on the location of cattle urine patches in pastures. The marker was tested in beef cattle kept on pastures under three grazing systems: degraded pasture under extensive management (De), intensively managed dryland pasture with high stocking rate (Id) and intensively managed irrigated pasture with high stocking rate (Ii). Besides the localization of urination sites, the number of urinations/animal/d and the area covered by urine were also determined. The residue of SF remained fluorescent in the pasture foliage up to 34 h after urination events, allowing the location of urine patches by a black‐light flashlight. There was no difference between grazing systems in the number of urine patches/animal/d during the rainy and dry seasons. The average number of urine patches was approximately 11/animal/d. As expected, the estimated volume and area covered by urine varied according to the stocking density. The chosen SF dose (50 mg kg^?1 LW) did not adversely affect the animals when administered once daily during 2 d. However, the same SF dose administered during four consecutive days caused urinary disorder in the animal. The distribution of urine patches was spatially dependent on specific characteristics of the paddock.     

Can light intensity influence the tolerance of Synedrellopsis grisebachii to glyphosate?

Plant susceptibility to herbicides is related to several factors, including the environmental conditions under which the plants develop. Two experiments were carried out using Synedrellopsis grisebachii plants in two different developmental stages (vegetative and reproductive), with the goal of studying plant susceptibility to the herbicide, glyphosate, and the dependence of this susceptibility on light intensity (full sunlight and 70% shading), correlated with leaf anatomy. The experimental design for both experiments was completely randomized, with a 2 × 7 factorial scheme, with two light intensities and seven different doses of glyphosate (0D, 1/4D, 1/2D, D, 2D, 4D and 6D, where D is the recommended dose of 1800 g ae ha^?1) as the factors and four replicates per treatment. The leaf anatomy was characterized with optical and scanning electron microscopy. The plants that were grown in full sunlight were more tolerant of glyphosate because of thickening of the adaxial epidermis, parenchyma and main vein structures, which required higher glyphosate doses for effective weed control. The plants that were in the reproductive stage were more tolerant of glyphosate, probably because of lower glyphosate absorption and translocation to the reproductive organs.