Antimicrobial activities and cytotoxicity of the brown alga Cystoseira tamariscifolia

The hexane, ethyl ether and dichloromethane fractions of the brown alga Cystoseira tamariscifolia extract showed interesting antimicrobial activities and cytotoxicity.     

Growth and survival model of Pacific bluefin tuna (Thunnus orientalis) for capture‐based aquaculture in Mexico

Capture‐based aquaculture (CBA) is a strategy to capture wild aquatic organisms for rearing. The most iconic species produced under this scheme are bluefin tunas. In Mexico, CBA of this species is developed with Pacific bluefin tunas (PBFT). The parametrization of a biological production function able to describe biomass dynamics during the production cycle is one of the strategies that can help optimize production. The objective of this study was to explain biomass dynamics in capture‐based Pacific Bluefin tuna aquaculture in Mexican waters through parameterization of a growth and survival model. This study also assessed the impact of uncertain intrinsic CBA variables (i.e. seed weight, number of stocked individuals and sea surface temperature [SST] variability). The model was parameterized with production records of 47 net pens in two production sites (an offshore and an inshore facility) during three cycles. The results suggested that production performance was related to SST given that this factor affected survival, mainly during the first ≈40 days after stocking. The risk analysis showed that stocking during the second half of the fishing season from June to August increased the likelihood of matching or exceeding the Key Performance Indicator (KPI) defined regarding biomass increase per pen.     

Total Mercury Bioaccumulation in Tissues of Carnivorous Fish (Micropogonias furnieri and Cynoscion acoupa) and Oysters (Crassostrea brasiliana) from Sepetiba Bay,Brazil

Total mercury (Hg) levels were determined by cold vapor atomic absorption spectrophotometry (CVAAS) in tissues of two species of carnivorous fishes and in the soft tissue of oysters caught in Sepetiba Bay, Brazil. Hg was distributed unevenly in the organs and tissues of the fish; the mean Hg content was highest in the kidneys (0.048 μg/g wet weight) and lowest in the gills (0.004 μg/g w.w.). Mean Hg levels were higher in the oysters (0.052 μg/g w.w.) than in the fish (0.022 μg/g w.w). The total Hg concentration did not exceed the maximum concentration for food allowed by Brazilian legislation in any of the fish and oyster samples analyzed. Moreover, the Hg concentrations observed were all within the maximum level for fish recommended by the Food and Agriculture Organization (FAO; 0.5 μg/g w.w.).     

First results on spawning, larval rearing and growth of the wedge sole (Dicologoglossa cuneata) in captivity, a candidate species for aquaculture

The wedge sole is a target species in the fisheries of the Gulf of Cadiz (Spain). Having reared them to commercial size, we have studied reproduction and breeding in captivity of the wedge sole in this work here. The breeders adapt easily to captivity, and they can spawn in less than 1 year in captivity. The relative fecundity is relatively high, 1.06–2.33 · 10⁶ eggs kg⁻¹ per spawning season (mean 1.6 ± 0.1). Larval SGR is high, 7.2 ± 0.2% day⁻¹ (range 5.8–9.1), similar to other cultured flatfish species. In 1 year, some individuals reach market size and can release eggs, registering SGRs of 1.39–1.66% day⁻¹ (mean 1.56 ± 0.01). This species presents some very different characteristics with respect to other farmed flatfishes (turbot, halibut and Senegal sole, mainly), so that it is necessary to develop new techniques to optimise its cultivation. In the present work, the first results are presented on the biology of the wedge sole in captivity.     

Cultivation of whitebait (Galaxias maculatus) in Chile

The growth of commercial aquaculture in Chile generated an income of $2.300 million USD in exports in 2005. Currently, 15 different species are cultivated commercially, of which seven are native; these had returns of 185 million USD. Among these native species is Galaxias maculatus (whitebait), which is endemic to Chile and figures significantly in Chilean fishing statistics. Since the 1990s, the School of Aquaculture of the Universidad Catolica de Temuco has been developing cultivation of this native species. This work presents the state of the art of the cultivation of this fish.     

Simple genetic inheritance conditions resistance to <Emphasis Type="Italic">Liriomyza sativae</Emphasis> in melon

The leafminer Liriomyza sativae (Diptera: Agromyzidae) stands out as the main plant health problem in melon in the Northeast region of Brazil, which is the main region for production and export of the fruit. Genetic resistance of plants is an important strategy in management of this pest. The plant BAGMEL 56-R was selected as a new source of resistance to L. sativae through antibiosis; this resistance is characterized by the death of larvae soon after they begin feeding on the leaf mesophyll; the result is leaf mines that are small and insignificant in terms of yield reduction. Lines with contrasting levels of resistance were obtained from the progenies of this source of resistance through successive self-pollinations, conducted by the pedigree breeding method. Through the segregation pattern of the progenies and the test cross, the genetic nature of resistance was determined; one gene with complete dominance conditions resistance. The name Liriomyza sativae resistance and the symbol Ls are suggested to represent this new gene. In addition, through a non-preference test with lines in contrast for antibiosis and the susceptible hybrid ‘Goldex’, the presence of antixenosis was observed in this source of resistance. Probably, these different types of resistance in the source BAGMEL 56-R are associated with distinct defense mechanisms. Therefore, with this new source, introgression of resistance to L. sativae in elite lines or commercial hybrids of melon is possible.     

Short-term impact of spent coffee grounds over soil organic matter composition and stability in two contrasted Mediterranean agricultural soils

Purpose

Spent coffee grounds (SCG) is a biowaste which arouse great interest as soil organic amendment due to the huge amount produced around the world. However, the impact of this residue on soil organic matter (SOM) functionality and stability has been barely studied. Thus, the aim of this work is to study the short-term effects of SCG on the quantity and quality of SOM in two Mediterranean agricultural soils (Vega soil, SV and Red soil, SR) in microcosm conditions.

Materials and methods

The in vitro assay was performed with two fresh SCG doses (2.5 and 10% w/w), two incubation times (30 and 60 days) and two agricultural soils (SV and SR). SOM fractionation to obtain total extractable carbon, humic acids, fulvic acids, humins and hot water soluble carbon (HWSC) was determined. Spectroscopic UV-Vis and Mid-IR, thermogravimetric and simultaneous differential thermal analysis, as well as scanning electron microscopy (SEM), were also applied in this study.

Results and discussion

SCG increased all SOM fractions, especially the levels of more labile SOM (HWSC, increased 600–700%) and total extractable carbon (increased to around 200%). SCG also increased humic acids and fulvic acids around 200%, but the functionality of humic acids was affected by a reduction of the functional groups with more recalcitrant and stable character. The tested soils are different from each other (the SV has a more clayish texture and a higher smectite clay content than the SR) which made the behaviour of these soils different. The degree of incorporation of SCG into the soils structure and the interaction between soil and SCG particles (observed by SEM) affected carbon retention under stable forms, increasing carbon stabilization in SV with respect to SR.

Conclusions

The short-term effect of SCG on SOM composition and functionality demonstrate that this bioresidue could be used as soil organic amendment, being a valuable alternative use of a polluting waste. Soil type is a key factor since it influences the soil-SCG interaction and consequently SOM stability. To deepen the study of those effects, it would be necessary to analyze the long-term effects, field studies and to test in a greater number of soil types.

     

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

Cercospora species cause cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean. Because there are few resistant soybean varieties available, CLB/PSS management relies heavily upon fungicide applications. Sensitivity of 62 Argentinian Cercospora isolates to demethylation inhibitor (DMI), methyl benzimidazole carbamate (MBC), quinone outside inhibitor (QoI), succinate dehydrogenase inhibitor (SDHI) fungicides, and mancozeb was determined in this study. All isolates were sensitive to difenoconazole, epoxiconazole, prothioconazole, tebuconazole, and cyproconazole (EC₅₀ values ranged from 0.006 to 2.4 µg/ml). In contrast, 51% of the tested isolates were sensitive (EC₅₀ values ranged from 0.003 to 0.2 µg/ml), and 49% were highly resistant (EC₅₀ > 100 µg/ml) to carbendazim. Interestingly, all isolates were completely resistant to azoxystrobin, trifloxystrobin, and pyraclostrobin, and insensitive to boscalid, fluxapyroxad, and pydiflumetofen (EC₅₀ > 100 µg/ml). The G143A mutation was detected in 82% (53) of the QoI-resistant isolates and the E198A mutation in 97% (31) of the carbendazim-resistant isolates. No apparent resistance mutations were detected in the succinate dehydrogenase genes (subunits sdhB, sdhC, and sdhD). Mancozeb completely inhibited mycelial growth of the isolates evaluated at a concentration of 100 µg/ml. All Argentinian Cercospora isolates were sensitive to the DMI fungicides tested, but we report for the first time resistance to QoI and MBC fungicides. Mechanism(s) other than fungicide target-site modification may be responsible for resistance of Cercospora to QoI and MBC fungicides. Moreover, based on our results and on the recent introduction of SDHI fungicides on soybean in Argentina, Cercospora species causing CLB/PSS are insensitive (naturally resistant) to SDHI fungicides. Insensitivity must be confirmed under field conditions.     

Stereo vision three-dimensional terrain maps for precision agriculture

The combined interest in precision agriculture, information technology, and autonomous navigation has led to a growing interest in the generation of 3D maps of mobile equipment surroundings. This article proposes a method to create 3D terrain maps by combining the information captured with a stereo camera, a localization sensor, and an inertial measurement unit, all installed on a mobile equipment platform. The perception engine comprises a compact stereo camera that captures field scenes and generates 3D point clouds, which are transformed to geodetic coordinates and assembled in a global field map. The results showed that stereo perception can provide the level of detail and accuracy needed in the construction of 3D field maps for precision agriculture and field robotics applications.